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The San Francisco 49ers have reportedly traded 2005 first-overall pick Alex Smith to the Kansas City Chiefs. In return, the 49ers would receive the Chiefs’ second-round pick in 2013 (No. 34 overall) and a conditional midround pick in the 2014 draft.

Smith would be the latest in a line of former 49ers quarterbacks who have moved to Kansas City:

• Joe Montana was traded from San Francisco to Kansas City in April of 1993. He led the Chiefs to a pair of playoff appearances in two seasons and advanced all the way to the AFC Championship Game in 1993.

• Steve Bono was a highly regarded backup in San Francisco when he was traded to the Chiefs in 1994. Bono became the Chiefs' starter in 1995 and led the team to a 13-3 record.

• Elvis Grbac spent his first four seasons with the 49ers before signing with the Chiefs as a free agent in 1997. Grbac spent four seasons as the Chiefs' starter before moving on to Baltimore.

• And now it's Alex Smith's turn. Drafted first overall by the 49ers in 2005, Smith led San Francisco to the NFC Championship Game in 2011 before Colin Kaepernick took over as starter in Week 11 of this season.

In terms of Total QBR, the trade makes a lot of sense from the Chiefs’ perspective. Smith was the seventh-most efficient quarterback in 2012 with a rating of 70.1.

The Chiefs, on the other hand, ranked 29th in QBR at 31.9. Only the Browns, Jets and Cardinals were worse last season.

One reason that Smith posted such a high QBR in 2012 is that he was an accurate passer who took care of the ball.

Smith led the NFL with a 70.2 completion percentage last season and, since 2011, has thrown an interception on just 1.5 percent of his pass attempts. Among qualified passers over that span, only Aaron Rodgers (1.3) has thrown interceptions at a lower rate.

In Kansas City, quarterbacks have not been nearly as secure with the ball. Chiefs quarterbacks committed 29 turnovers in 2012, including 20 interceptions. The 29 turnovers trailed only the Jets (33) for most in the NFL and the 20 interceptions were one shy of the league-leading Cardinals (21).

Kansas City also threw a league-low eight touchdown passes in 2012, the fewest in a single season by any team since the 2007 Oakland Raiders (seven).

Alex Smith threw 13 touchdown passes in just nine games last season and his 30 touchdowns since 2011 are nine more than Chiefs passers have thrown over the same span.

Will the move pay immediate dividends? AccuScore seems to think so. According to 10,000 computer simulations, Alex Smith is worth approximately 2.2 wins for the Chiefs in 2013 and improves their chances of reaching the playoffs from 0.2 percent to 8.8 percent.

All that said, Smith will be forced to start from scratch in 2013. Doug Pederson will be the eighth offensive coordinator that Smith has played under in just his ninth season in the league. The past two seasons marked just the second time in his career that he had the same coordinator to begin consecutive NFL seasons.

Today is Valentine’s Day, when the thoughts of young football fans turn to ... well ... more football.

Stats & Information looks at some NFL couples and lets you know who should stay together, who needs to rebuild their relationship and who might want to spend some time apart.

COUPLES WHO NEED TO STAY TOGETHER
• Tom Brady and Wes Welker: Free-agent-to-be Welker has 672 receptions since joining the Patriots in 2007, the most for a player over any six-year span in NFL history.

• Eli Manning and Victor Cruz: Cruz, who is slated to become a restricted free agent, has 168 receptions and 19 touchdowns over the last two seasons. Along with Hakeem Nicks, he gives Manning one of the game’s best deep threats in the league.

• Matthew Stafford and Calvin Johnson: Johnson set an NFL single-season record with 1,964 receiving yards in 2012, while Stafford set an NFL record with 727 pass attempts. These two need to stay together if only to torture statisticians everywhere.

COUPLES WHO NEED TO REBUILD THEIR RELATIONSHIP
• Tony Romo and Dez Bryant: Early in the season, they didn't appear to be on the same page, but Bryant caught a league-high 10 TD passes from Week 10 until the end of the season.

• Aaron Rodgers and Jermichael Finley: Finley caught a career-high 61 balls in 2012, but just two went for touchdowns. At times it appeared that Rodgers had lost confidence in his tight end and reports have appeared that the Packers might release Finley.

• Cam Newton and Steve Smith: Smith was critical of Newton's sideline demeanor last season, and he could have a point. When trailing in the fourth quarter over the last two seasons, Newton’s QBR of 35.9 is 35th among 45 qualifying quarterbacks.

COUPLES WHO MIGHT NEED TO SPEND SOME TIME APART
• Mark Sanchez and Rex Ryan: After going to a pair of AFC Championship games in their first two seasons together, the relationship hasn't worked recently. Sanchez regressed even further in 2012, and has an NFL-high 52 turnovers over the last two seasons.

• Alex Smith and Jim Harbaugh: Harbaugh has turned to the younger Colin Kaepernick. Since Kaepernick took over as the starter in Week 11, his 81.2 Total QBR is second to only Russell Wilson. Smith’s QBR of 54.1 since the start of 2011 is 19th among quarterbacks with at least 500 action plays.

• Matt Cassel and Andy Reid: The Chiefs and Reid’s Eagles were tied with the Jets for the most turnovers in the NFL last season with 37. Cassel struggled with 19 turnovers in just nine games.

Colin Kaepernick took over as the San Francisco 49ers' starting quarterback in Week 11 after Alex Smith was sidelined with a concussion in the previous week. Since stepping in, Kaepernick has led the Niners to a 7-2 record and their first Super Bowl appearance in nearly 20 years.

He's not the first backup quarterback to lead his team to the Super Bowl after riding the pine early in the season. In fact, Kaepernick will be the sixth quarterback to start a Super Bowl after not starting any of his team's first five games of the same season. The others:

• Terry Bradshaw, 1974 Pittsburgh Steelers:
Bradshaw attempted a pass in just one of Pittsburgh's first six games of the 1974 season, playing behind Joe Gilliam. Bradshaw took over as the starter in Week 7 and went on to lead Pittsburgh to a win in Super Bowl IX, the first of four Super Bowls the Steelers would win in a six-year span.

• Vince Ferragamo, 1979 Los Angeles Rams
Ferragamo made his first start of the season in Week 12 for the Rams after Pat Haden was injured and Jeff Rutledge was benched. Ferragamo led the Rams to six wins in seven games on the way to Super Bowl XIV, where they fell to the Steelers.

• Jim Plunkett, 1980 Oakland Raiders
Plunkett took over after starter Dan Pastorini broke his leg during Week 5. Though Oakland was just 2-3 when Plunkett made his debut, the former Heisman Trophy winner took the Raiders to Super Bowl XV on the strength of nine wins in their final 11 regular-season games. Plunkett took home Super Bowl MVP honors after a 27-10 win over the Eagles.

• Jeff Hostetler, 1990 New York Giants
Hostetler replaced Phil Simms after the Giants star quarterback broke his foot in Week 15. Hostetler, a career backup, had started just two games in four prior NFL seasons. But that didn’t stop him from leading New York to five straight wins overall, including a 20-19 victory over the Buffalo Bills in Super Bowl XXV.

• Trent Dilfer, 2000 Baltimore Ravens
Dilfer stepped in for Tony Banks in Week 9 after the Ravens' offense was held without a touchdown for four straight weeks. After losing in his first start, Dilfer's Ravens won their final seven regular-season contests and went on to win each of their four postseason games by double digits, including a 34-7 drubbing of the Giants in Super Bowl XXXV.

By many accounts, Alex Smith had a pretty good year.

Smith was the only qualified quarterback in the league to complete more than 70 percent of his passes this season, throwing 13 touchdowns and five interceptions in his nine games as a starting quarterback. Smith’s 70.1 Total QBR was the sixth-best mark in the league, ranking higher than 27 of the league’s most current 32 starters.

So why will Smith be watching the NFC Championship from the sideline? One of those five starters ahead of Smith is teammate Colin Kaepernick, whose 81.5 Total QBR is the second-best in the league.

Kaepernick’s impact on San Francisco’s rushing game has been well documented, with zone-read option rushes added to the 49ers’ playbook since Kaepernick took over. As a pure passer he still presents an upgrade over his predecessor.

At first glance Kaepernick and Smith have similar passing numbers -- they both completed 153 passes and posted TD-Int differentials of +8.

However, Kaepernick has completed the same amount of passes as Smith in one fewer start despite an average pass length of 9.7 yards downfield, the fourth-highest average in the league. Smith’s 7.4 average throw distance ranks sixth-lowest among qualified quarterbacks.

Kaepernick has also connected on 15 plays of at least 30 yards this season, more than twice as many as Smith (six).

His willingness to stretch the field has made the 49ers a more dangerous and balanced offense. He's averaged more than twice as many throws more than 20 yards downfield as Smith did, but has protected the ball well. Kaepernick and Smith each have one interception on deep throws this season.

No one has benefitted more from Kaepernick’s willingness to take shots downfield than Michael Crabtree. Smith never relied on wide receivers heavily, a tendency highlighted in last year’s NFC Championship -- San Francisco wideouts finished with just one catch for three yards.

In his first nine games this season with Smith as starter, Crabtree tied for 41st in the league with 59 targets, was 39th with 510 receiving yards, and his average target depth was 6.4 yards downfield, the third-lowest of 76 qualified wide receivers.

Since Kaepernick became the starter in Week 11, Crabtree is fifth in catches (50), fourth in receiving yards (714) and tied for second with seven touchdowns.

One other difference between Kaepernick and Smith is highlighted when the play breaks down. Smith took a sack every 10.6 dropbacks, the worst mark in the league. Kaepernick is sacked every 17.4 dropbacks, which is 13th among 36 qualified quarterbacks.

Instead of taking sacks, Kaepernick extended plays with his legs. Kaepernick’s Total QBR under duress or when being hit while throwing this season was 53.3, fifth-best in the league, and an improvement on Smith’s 15.7 mark.

As a reminder, Total QBR is a quarterback rating that takes into account all of a QB’s significant contributions (passing, rushing, sacks, fumbles, penalties) to his team’s scoring and winning and summarizes them into one number on a 0-100 scale, where 50 is average. Since the start of 2008, the team with the higher QBR has won 86 percent of the time.

Russell Wilson posted a 99.3 Total QBR in Sunday's win over the Buffalo Bills, the highest single-game QBR this season.

Wilson did much of his damage with his legs, rushing for career-highs in both yards (92) and touchdowns (3).

His QBR followed suit because he added 9.5 points above average (PAA) on his running plays, the highest single-game total by any quarterback over the past five seasons. Even more remarkably, he did it on just nine carries.

The big game Sunday was just another in a string of strong performances -- since the start of Week 8, no player has a higher Total QBR than Wilson (87.9). That's due to his performance on deep throws and his ability to avoid turnovers.

Since Week 8, only Robert Griffin III (1) has fewer turnovers than Wilson (3) among qualified QBs and Wilson is in the top four in the league in completion percentage (54.8) and TD percentage (9.7) on throws of 10 or more yards.

QUICK HITTERS
• Colin Kaepernick posted an 87.1 Total QBR in Sunday night’s win over the New England Patriots, his fifth straight game with a QBR of at least 60 since becoming the 49ers' starter in Week 11. Kaepernick is second in the NFL in Total QBR this season (79.5) and 49ers backup Alex Smith (70.1) is seventh.

• Aaron Rodgers had an 83.0 Total QBR in Sunday's win over the Chicago Bears, his third straight game with a QBR of at least 80. Rodgers entered Week 15 tied with Drew Brees for most games with a QBR of 80 or higher over the past two seasons.

• Matt Schaub posted a season-high 90.4 Total QBR against the Indianapolis Colts, his highest since Week 10 of last season against the Buccaneers (92.0). With the win, the Houston Texans improve to 17-2 in games in which Schaub has a QBR of 85 or better over the past five seasons.

• Matt Ryan had a 96.2 Total QBR in Sunday's win over the New York Giants, his third game with a QBR of at least 95.0 in 2012. That's tied with Tom Brady for the most such games in the NFL this season.

TOTAL QBR AND WINNING
Total QBR can be used to quantify just how important the quarterback position has become to winning in the NFL. Looking back to previous years, the team with the higher Total QBR has won 86 percent of regular season games since 2008 (as far back as Total QBR goes). That is higher than the comparable mark for teams with the advantage in total yardage, turnover differential, and NFL passer rating.

Colin Kaepernick was conservative and at times overwhelmed by pressure in Week 13.

His average pass length was 5.8 yards downfield against the St. Louis Rams, a substantial decrease from how he aired it out in his first two starts.

Kaepernick had one pass gain more than 30 yards in the game after five such plays in his first two starts.

A deeper dive into the game using coaches’ film (which shows all 22 players on the field) reveals how the Rams’ defensive strategy dictated the 49ers’ conservative passing attack.

How the Rams took away Kaepernick’s arm

Kaepernick faced at least five pass rushers on 24 of 40 (60 percent) dropbacks against the Rams. That is the highest percentage of pressure the Rams have sent in a game over the last two seasons.

With fewer defenders in coverage because of additional pass rushers, the Rams provided the 49ers with plenty of cushion to sacrifice underneath throws rather than big plays. Specifically, their cornerbacks gave 49ers wide receivers at least five yards of space with no jam coverage on 33 of Kaepernick’s 40 dropbacks.

The 49ers adjusted to the Rams’ strategy by getting the ball out of Kaepernick’s hands quicker and keeping their routes short to avoid pressure and take what was open.

In the first quarter, the 49ers ran multiple routes further than 15 yards downfield on five of seven passing plays. After realizing they would not find the same downfield success as in Kaepernicks’ previous two starts, the 49ers had multiple receivers running such deep routes on six of 27 passing plays the rest of the game (excludes passing plays inside 10 yard line).

On average, Kaepernick released his pass 3.2 seconds after the snap, compared with 4.2 seconds in Week 12 against the Saints.

The Rams also bottled Kaepernick up when he escaped pressure and left the pocket (excluding his 50-yard scramble in the fourth quarter).

When outside the pocket, Kaepernick failed to complete any of his three passes, was sacked twice and was flagged for intentional grounding that resulted in a safety.

How will the Dolphins fare on Sunday in containing Kaepernick?

The Dolphins have allowed the second-highest completion percentage and Total QBR to quarterbacks on plays outside of the pocket this season.

Russell Wilson exposed the Dolphins’ problems against athletic quarterbacks in Week 12, completing 8-of-9 passes outside the pocket with a touchdown. Earlier this season, Andrew Luck completed all six of this passes outside the pocket for 89 yards against Miami.

While the Dolphins may struggle containing Kaepernick, he will have to make adjustments as defenses continue to adapt to his strengths.

The pressure isn’t going away, as no quarterback has seen a higher percentage of dropbacks against at least five pass rushers this season. Kaepernick hasn’t handled the pressure as well as Alex Smith, who has completed a league-best 72.2 percent of his passes against such pressure.

The San Francisco 49ers didn’t miss a beat by having Colin Kaepernick start against the New Orleans Saints on Sunday. Kaepernick completed 64 percent of his throws in Sunday’s win. Coincidentally, that was a match for Smith’s completion percentage over the last two seasons.

Also of note from Kaepernick’s performance.

1-Outside-the-pocket success: Kaepernick was 5-for-7 for 54 yards and a touchdown on throws made outside the pocket.

For the season, Kaepernick is 11-for-18 with three touchdowns and no interceptions on his outside-the-pocket throws. Smith is 9-for-19 on such throws with one touchdown and one interception.

Kaepernick has converted first downs nine times on his 18 outside-the-pocket throws. Smith has converted only four of 19.

2-Comfortable with play action: Kaepernick was 7-for-10 for 125 yards and a touchdown on his play-action pass attempts, converting first downs on all seven of those completions.

He was 9-for-15 for 107 yards on his other throws, converting three first downs. The play-action was aided by the 49ers averaging nearly five yards per rush.

3-Outplayed Drew Brees: Though Brees threw for three touchdowns, he had a rough game, with two interceptions returned for scores the other way (the first time the 49ers had multiple interception returns for touchdowns in a game since 1995).

Brees finished the day 2-of-9 for 76 yards and an interception on throws deeper than 10 yards downfield, his worst completion percentage on those throws in the last five seasons.

Sunday was the first time this season Brees had more overthrown passes (three) than completions (two) on those throws.

Though Kaepernick had an interception of his own, he was 4-for-8 for 98 yards on throws of that length. That included a pair of third down completions to Delanie Walker, extending drives that resulted in a touchdown and a field goal.

Kaepernick finished the day with a Total QBR of 72.3 Kaepernick's Total QBR of 85.0 the last two weeks is the second-best total by any quarterback in his first two career starts within the last five seasons. The only quarterback better-- Aaron Rodgers (86.1)

What has been the key to the Chicago Bears defensive success this season?

In recent years, the Bears have primarily played a split-safety Cover 2 formation with two defenders in the secondary. This season, they have utilized a single-high safety with fantastic results.

A single-safety defense is defined as one that has one safety deep in pass coverage. The split-safety defense is defined as two safeties ‘split’ deep in coverage.

The idea behind one deep safety as the last line of defense is that the second can be used at the line of scrimmage. It’s important to have cornerbacks who can cover 1-on-1 downfield for a single-safety defense to be effective. Tim Jennings has done just that for the Bears, leading the league with five interceptions on throws more than 10 yards downfield, including three when they are in single-safety coverage.

Let’s take a look at what our video review showed on the Bears defensive excellence. We broke down every coverage used by the Bears excluding penalties, spikes, a fake punt and plays inside the 10.

What the numbers show...

The Bears have balanced their secondary coverage, using a single-high safety on slightly more than half of the pass attempts.

With the Bears having played several blowouts, it’s important to note that when the score has been within one possession, the Bears prefer single-safety coverage on 64 percent of pass attempts.

The Bears single-safety defense is holding opposing quarterbacks to a much lower completion percentage (-14.4 percent) as noted in the chart on the right.

The most noticeable impact is in the short passing game, where the Bears single-high safety has held opponents to a 59 percent completion rate on throws 10 yards or fewer, with five interceptions and no touchdowns.

Their split-safety defense has allowed nearly 75 percent of such throws to be completed.

Looking ahead to Monday Night

The last time Chicago and the San Francisco 49ers met, the Bears "loaded the box" on nearly half of the defensive plays (45 percent), their fourth-highest single game percentage in the last four seasons. In that contest, 49ers quarterback Alex Smith was sacked twice and threw his only interception against a loaded front.

No team in the NFL has used a “loaded front” on defense more often than the Bears (28 percent of plays). A “loaded” box is identified when the defense has more players in the ‘tackle box’ than the number of available blockers on offense.

While evidence suggests Chicago will utilize the single-high formation and load the box often on Monday, they might want to be weary of Colin Kaepernick’s strong arm. His average throw has traveled 10.5 yards downfield this season, the furthest in the league among quarterbacks with at least 20 attempts.

The 49ers backup has completed seven of 10 attempts traveling more than 10 yards downfield in his limited time this year, while the league average completion percentage on such throws is 48.9 percent.

Kaepernick could challenge the Bears loaded front downfield, but it should limit his scrambling. He has been quick to run this season, scrambling on seven of his 38 dropbacks (18.4 percent), the highest scramble rate in the league (minimum 10 dropbacks).

We know that two backup quarterbacks will start this week, and as many as four. Here’s a look at what they’ve done in the limited playing time.

NICK FOLES, PHI (34.9 Total QBR in Week 10)

Nick Foles went 22-of-32 with a touchdown and an interception in his NFL debut last week. Although Foles threw only one interception (which was returned for a TD), it could have been worse. Foles had two potential interceptions dropped and another interception called back due to a penalty. It was the fourth time this season that a quarterback had multiple interceptions dropped in game. It wasn’t all bad for Foles. He connected on 4-of-6 attempts more than 10 yards downfield, with two of those completions gaining 30-plus yards. Michael Vick had two 30-plus yard plays in a game only twice this season.

BYRON LEFTWICH, PIT (61.7 Total QBR in Week 10)

In his limited playing time since the start of 2008, Byron Leftwich has posted a 52.2 Total QBR, which means he has played at an average level. If there’s one area in particular that Leftwich has performed below average during that time, it’s on deep throws. Leftwich hasn’t completed a pass more than 20 yards downfield since Week 2 of the 2009 season when he was with the Tampa Bay Buccaneers, and has completed just 4-of-21 attempts of more than 20 yards downfield since the start of 2008. That’s the third worst completion percentage of any quarterback with at least 20 attempts.

JASON CAMPBELL, CHI (21.7 Total QBR in Week 10)

Similar to Leftwich, Jason Campbell’s 50.9 Total QBR over the last five seasons puts his performance at an average level, but he may be able to capably fill Jay Cutler’s void. The San Francisco 49ers have sent four or fewer pass rushers 78.8 percent of the time since the start of last season, that’s the second-highest rate in the NFL. Both Cutler and Campbell have posted Total QBRs over 60.0 against such pressure, with Campbell actually posting a better completion percentage.

Don’t expect Campbell to air it out too often, though. Of the 30 quarterbacks with at least 1,000 attempts in the last five seasons, Campbell’s 6.6 yard average throw distance ranks as the shortest. Cutler’s 8.2 average is tied for the ninth highest.

COLIN KAEPERNICK, SF (40.7 Total QBR in Week 10)

Colin Kaepernick’s biggest strength so far this season has been running the ball. Kaepernick has averaged 8.8 yards per rush on 14 designed runs. That rate is best among quarterbacks, and 3.8 yards higher than Cam Newton’s 5.0 designed yards per rush average. However, Kaepernick might be too quick to run on pass plays this season, scrambling on seven of his 38 dropbacks (18.4 percent). Not only is that the highest scramble rate in the NFL (minimum 20 dropbacks), but it’s nearly double that of the next highest quarterback (Robert Griffin III, 9.7 percent).

Some of the success that the San Francisco Giants pitchers had in helping their team to a World Series title rubbed off on their football counterpart.

San Francisco 49ers quarterback Alex Smith had the best day of his career, one that was Joe Montana and Steve Young-like in terms of statistical accomplishments.

For much of the night, it looked like Smith was playing a game of catch with his receiving teammates. Giants pitchers had what baseball folks call “swing-and-miss” stuff. Smith had can’t-miss stuff.

Let’s look some of the highlights of the 49ers easy win over the Arizona Cardinals.

Just shy of perfection
Smith was 18-for-19 on his pass attempts, setting a mark for passes thrown in a game with no more than one incompletion. The Elias Sports Bureau tells us that the previous mark of 18 was set by Fran Tarkenton in 1977 and matched by Craig Morton in 1981.

Montana’s most accurate day, with at least that many pass attempts, was an 84.4 percent success rate, when he went 27-for-32 against the Falcons in 1983.

Montana’s fewest incompletions in a game with as many attempts as Smith was three. He went 16-for-19 against the Falcons in 1989.

Young’s best was two incompletions, in an 18-for-20 game against the Detroit Lions in 1991. He also had a 15-for-16 game in 1994, as noted in the chart above.

What was the key to Smith’s performance?

Smith was 7-for-8 for 113 yards when the Cardinals sent at least five pass rushers, the only incompletion being a drop by Delanie Walker.

His level of success against that kind of pressure isn’t that surprising. Smith entered the day with the fourth-best Total QBR in the NFL against pass rushes of five or more defenders.

Milestone for Moss
49ers receiver Randy Moss looked like his old self on a 47-yard touchdown reception in the third quarter. It was Moss’ 156th career touchdown, tying Terrell Owens for fourth-most all-time.

Moss has 18 touchdowns in 19 appearances on Monday Night Football, with five of them going for at least 40 yards.

His 18 receiving touchdowns are third-most all-time, trailing Jerry Rice’s 34 and Terrell Owens’ 20.

Moss has 45 touchdown receptions that gained at least 40 yards, easily the most by anyone currently playing in the NFL. Santana Moss ranks second with 20.

The defense had a good game too
The 49ers defense held the Cardinals to three points. It marked the fourth time in the last five games that the 49ers allowed six points or fewer. San Francisco’s four such games are the most for all NFL team since the 49ers themselves had five in 2009.

First place in the NFC West will be on the line when the Arizona Cardinals host the San Francisco 49ers tonight on Monday Night Football at 8:30 ET on ESPN.

It's a meeting of two of the league's best defenses. The 49ers currently lead the league in fewest yards allowed per game (272.3) and are tied for first in points allowed per game (14.3). The Cardinals are sixth in yards (312.1) and fourth in points (16.9).

This will be the sixth Monday Night Football meeting between these teams, with the 49ers winning four of the previous five.

49ers KEYS TO VICTORY
The key for the 49ers on the offensive side will be their running game. Under Jim Harbaugh, the 49ers are 17-0 when they run the ball at least 25 times and 1-5 when they don’t.

If they maintained their current average of 5.9 yards per carry, it would be the NFL's highest single-season mark since the merger.

The other key is reducing turnovers, particularly with their quarterback. Alex Smith led the NFL with a Total QBR of 81.1 through Week 5, but his last two games haven't been so good. Smith has thrown five interceptions this season (including four in last two games), matching his total for all of 2011.

Perhaps one of the reasons for Smith’s recent struggles is due to a sprained finger in Week 5 against the Buffalo Bills. Since that game, his downfield throwing has taken a hit. Smith has gone 5-of-13 (38.5 percent) on throws more than 10 yards downfield his last two games (third-worst), after leading the NFL in completion percentage on such throws (59.5) through the first five weeks of the season.

CARDINALS KEYS TO VICTORY
The key for the Cardinals will be protecting their quarterback John Skelton.

The Cardinals have allowed a league-high 35 sacks (seven more any other team). Arizona's passers have now been sacked 29 times in their last four games, the most suffered by any NFL team over a four-game span since the Cardinals themselves were sacked 29 times over four games in November 1997 (according to Elias).

Skelton hasn’t been particularly great.

Skelton has thrown an interception in 10 straight games, the longest active streak in the NFL.

Skelton has completed just 44.4 percent of his attempts to Larry Fitzgerald more than 10 yards downfield this season, while Kevin Kolb has completed 62.5 percent of such passes this season.

But the Cardinals defense has kept them in games this season. They’re the only team to hold each opponent this season to 21 points or fewer.

After the New England Patriots fell behind the St. Louis Rams 7-0, quarterback Tom Brady took over the game as the Patriots outscored the Rams 45-0 the rest of the way.

Brady’s 98.4 Total QBR on Sunday is tied for his highest in a single game over the last five seasons and is the second-highest for any player in 2012, trailing only Alex Smith's Week 5 performance that netted him a 99.2 Total QBR.

Brady has had a penchant for stepping up in big games on the road the last few seasons. Sunday marked the seventh time he’s had a Total QBR above 90 in a road game since 2010 – most in the NFL.

ANOTHER ROUGH DAY FOR MARK SANCHEZ
On the opposite end of the spectrum from Brady is New York Jets QB Mark Sanchez. In the Jets’ 30-9 loss to the Dolphins, Sanchez had a Total QBR of 12.1. Since coming into the league in 2009, Sanchez has had 12 games in which his Total QBR was under 15 – most in the NFL.

To put those struggles in some perspective, Brady, Aaron Rodgers, Peyton Manning and Drew Brees have combined to have one game with a sub-15 Total QBR in that span.

QUICK HITTERS
• Tony Romo dug himself a hole when he posted a Total QBR of 3.3 in the first half of Sunday’s loss against the Giants (27 action plays). Since 2008, only Andy Dalton in Week 4 of last season has posted that low of a first-half QBR with at least 25 action plays and gone on to win the game.

• Matt Ryan had a 95.7 Total QBR in the Falcons’ win against the Eagles, his highest since Week 1 against the Chiefs (97.5). Ryan entered the game with a 45.3 career QBR against Philadelphia, his worst against any team he had faced at least twice previously.

• In their Sunday night matchup, Peyton Manning had a 96.3 Total QBR and Drew Brees posted a 24.2. Manning’s QBR was his highest since Week 15 of 2009 and his second-highest over the last five seasons. Brees’ QBR was his lowest since Week 7 of 2010 and his third-lowest over the last five seasons.

• Ben Roethlisberger posted a 90.2 Total QBR in Pittsburgh’s win over the Redskins, his third game with a QBR of 90 or better in 2012. Roethlisberger had no more than two such games in any of the previous four seasons.

• Russell Wilson had a career-high 93.7 Total QBR in Seattle’s loss to the Lions. It’s the highest QBR by a player in a loss since Matt Cassel in 2010 (Week 6 - 93.8) and the fourth-highest in a loss over the last five seasons.

TOTAL QBR AND WINNING
Total QBR can be used to quantify just how important the quarterback position has become to winning in the NFL. Looking back to previous years, the team with the higher Total QBR has won 86% of regular season games since 2008 (as far back as Total QBR goes). That is higher than the comparable mark for teams with the advantage in total yardage, turnover differential, and NFL passer rating.

Keep in mind that just because a team wins a game with a lower QBR than its opponent does NOT mean that Total QBR was “wrong” or not as good for that game. That just means that the winning team was able to overcome its QB being outperformed by the opposing QB (on a rate basis), usually by playing better in other aspects of the game (rushing game, special teams, etc.).

Complete QBR statistics for all quarterbacks can be found here..

On Wednesday, ESPN Stats & Info debated which defense has been more impressive in 2012, the Seattle Seahawks or San Francisco 49ers?

But what about the leaders -- specifically the quarterbacks -- on the other side of the ball?

At 4-2, Seattle's Russell Wilson is the only one of the five starting rookie QBs who has a winning record.

His first start of the season was on the road against the Arizona Cardinals, and he went 1-of-3 with an interception on throws more than 20 yards downfield. In the five games since, Wilson is 9-for-16 with five touchdowns on such throws. However, the 49ers defense that has yet to allow a score this season on the deep ball.

Wilson has not been the same QB on the road as he has at home. All six of his interceptions have come on the road and his Total QBR ranks 25th at 30.0. Overall, the Seahawks are averaging 15.0 points per game on the road. In fact, Seattle’s offense has not scored more than 16 points in any of its three road games.

So not only have the Seahawks been a different team on the road, but they're playing a 49ers club that has been on roll at home against NFC West opponents.

The 49ers have won 10 straight home games against divisional opponents, the longest active streak in the NFL and the 49ers longest streak since 11 straight home divisional wins from 1991-95.
San Francisco's starting QB, Alex Smith, is coming off a three-interception game in Week 6, snapping a streak of 26 straight games without throwing multiple interceptions.

One indicator of Smith’s success this season has been his effectiveness throwing the ball more than 10 yards downfield (see chart). In 2012, Smith already has thrown more interceptions on throws more than 10 yards downfield (four) than he did all of last season (three).

Both the 49ers and the Seahawks have solid running backs who are coming off their worst games of the season.

Frank Gore had just 36 yards Sunday against the New York Giants, and Marshawn Lynch rushed for 41 yards against the New England Patriots. Last season, however, Lynch rushed for 107 yards in Week 16 against the 49ers. He’s one of only two running backs since the start of 2010 who has rushed for 100 yards against San Francisco. (The other was Ahmad Bradshaw last week.)

Can Gore get back on track against Seattle’s defense, which ranks second against the run this season? Gore has 18 rushes this season of at least 10 yards, which is tied for most in the NFL with the Washington Redskins Alfred Morris. However, the Seahawks have allowed just 10 runs of at least 10 yards this season, that’s tied for second-fewest in the league.

Robert Griffin III posted the highest single-game Total QBR of his career on Sunday (97.6). It was the third-highest by any rookie quarterback over the last five seasons.

His performance was also the best by a Washington Redskins quarterback in a single game since 2008, a few points higher than the 93.8 he posted in his debut against the New Orleans Saints earlier this season.

BRADY, PATRIOTS UNABLE TO HOLD LATE LEAD IN SEATTLE
The New England Patriots had the lead late in the fourth quarter before the Seattle Seahawks scored a go-ahead/game-winning touchdown with 1:18 to play.

Including the postseason, it was the seventh time since 2009 the Patriots lost a game in which it held a lead in the final five minutes of regulation, which is tied for third-most in the NFL.

Part of the blame can be directed at Tom Brady, who has not performed well when attempting to hold leads of eight points or fewer over that span.

Among 17 players with at least 10 action plays in the final five minutes of regulation with a one-score lead, not many have a lower Total QBR than Brady since 2009.

QUICK HITTERS
• Eli Manning had a season-high Total QBR of 96.0 against the San Francisco 49ers, his highest since he posted 98.3 in a win against the Seahawks in Week 9 of 2010. It was his third game this season with a Total QBR of 90 or better, tied with his brother Peyton for the most in the NFL.

• Alex Smith had a 24.8 Total QBR in the loss to the New York Giants, his lowest since Week 14 of last season. This comes just one week after Smith posted the highest single-game Total QBR for a 49er quarterback and fifth-best for any player over the last five seasons (99.2 vs Buffalo).

" Andrew Luck entered Week 6 with a league-best 90.4 Total QBR in the first half this season with four touchdowns and an interception. Luck posted a 53.2 in the first half of Sunday’s loss to the New York Jets with no touchdowns and a pick.

TOTAL QBR AND WINNING
Total QBR can be used to quantify just how important the quarterback position has become to winning in the NFL.

Looking back to previous years, the team with the higher Total QBR has won 86 percent of regular season games since 2008 (as far back as Total QBR goes). That is higher than the comparable mark for teams with the advantage in total yardage, turnover differential, and NFL passer rating.

Keep in mind that just because a team wins a game with a lower QBR than its opponent does not mean that Total QBR was "wrong" or not as good for that game.

That just means that the winning team was able to overcome its quarterback being outperformed by the opposing signal caller (on a rate basis), usually by playing better in other aspects of the game (rushing game, special teams, etc.).

Complete QBR statistics for all quarterbacks can be found here.

At the end of Week 5, Alex Smith is the leader in Total QBR. Let me say that again for San Francisco 49ers fans who have endured some tough quarterback play in recent seasons; Alex Smith is the most efficient quarterback in the league through five games.

Before this season, no 49ers quarterback had led the league in QBR at the end of any week in the QBR era (since 2008).

How is he doing it?

Usually a good QBR can be attributed to a few key factors, two of which are performing well on third downs and when the game is late and close. Smith, however, is actually not performing that well in either situation.

On third downs he has a 37.4 QBR, 20th-best among the 33 qualified quarterbacks. In clutch situations –- defined as the fourth quarter or overtime with the game within eight points –- he isn’t much better, ranking 15th in QBR among the 29 quarterbacks with at least 10 action plays.

So it’s clearly not third downs and it’s not performing well in the clutch. For Smith it’s actually what he’s doing on the early downs while the defense is crowding the line to stop the 49ers running backs.

He is torching defenses on first and second downs with at least seven defenders in the box, posting a 96.3 QBR -– three points better than any other quarterback. This is a marked improvement for Smith, who was not able to take advantage of run-preventing defenses in the past.

A lot of his success on these plays has come by throwing the ball over the top of aggressive defenses. On throws at least 15 yards downfield in these situations, Smith is 10-for-16 with two touchdowns and no interceptions and is one of three QBs with a 100.0 QBR.

This has led to increased effectiveness for Frank Gore and the San Francisco running game as well. From 2009 to 2011, the 49ers averaged 4.3 yards per rush while attaining a first down on 18 percent of rushes on first or second down with at least seven defenders in the box.

Those were roughly league average numbers.

This season, the 49ers are averaging 6.1 yards per rush and getting a first down on 30 percent of rushes in these situations. Against the Buffalo Bills on Sunday, the numbers increased to 8.2 yards per rush with 37 percent gaining enough for a first down.

It’s not often that a quarterback can be so average in higher leverage situations and have such a good QBR.

But if Alex Smith can continue to take advantage of defenses not respecting him on early downs, he and the 49ers should continue to be one of the best offenses in the league.