Detroit, San Francisco ... playoffs ?

Going into the season, who would have thought Sunday's San Francisco-Detroit game would have such impact?

The 49ers haven't made the playoffs since 2002. The Lions have been out of the playoffs since 1999. Both teams are in the thick of the playoff hunt now thanks to a 4-1 start by the 49ers and a 5-0 start (and nine-game regular-season winning streak) for the Lions dating to last season.

Jim Harbaugh's challenge in this game is trying to hold down the Lions' offense. Matthew Stafford is healthy and playing like a stud. He's thrown for 13 touchdowns, including nine to Calvin Johnson. And Stafford's rallied his team from 20- and 24-point deficits on the road.

With six home games left and a loud Ford Field crowd, the Lions aren't just thinking about a wild-card berth. They are thinking about challenging the Packers for first place in the NFC North.

Harbaugh is doing plenty with fewer weapons. Mike Singletary left him a good defense, and defensive coordinator Vic Fangio is doing a great job coaching it. But Harbaugh has been the master of getting the most out of Alex Smith, who is in his seventh year in San Francisco. While Stafford is going for the big play, Smith is trying to get the most out of little throws.

Ninety-four of his 126 pass attempts went 10 yards or fewer in the air, according to ESPN Stats and Information. None of them have been intercepted, which is the key to Harbaugh's offense. He knows he can get yards out of Frank Gore. He knows the defense will keep the 49ers in games.

Smith will be handcuffed to a certain extent because he'll be without two of his top three receivers, Braylon Edwards and Josh Morgan. That will force the 49ers to go more with two tight ends and allow the Lions the chance to double-cover Michael Crabtree.

Here are the 10 top trends and stories for Week 6:

1. Win or go home: The focus in Sunday's Philadelphia-Washington game will be on Andy Reid. The Eagles are 1-4. The Redskins are 3-1 and have the easiest non-divisional schedule in the NFC East. If the Eagles lose and fall 3 games behind the Redskins, it will be almost impossible for the Eagles to catch them for the divisional lead or a wild-card spot. The Lions are sitting at 5-0 in another division, which means the bar for those wild-card spots will be pretty high. The Eagles are a mess. The run defense is giving up 140 yards a game and 5 yards a carry. The high-priced defense has forced only five turnovers in five games. In his last seven starts, Michael Vick is 1-6 and has 14 turnovers. It's hard to imagine the Eagles firing Reid at the end of the season. He's a coaching icon in Philadelphia. But Eagles management was thinking Super Bowl, not also-ran. It's vital for the Eagles to win.

2. Bad timing for the Houston Texans: They figured to have their passing offense drop about 30 yards last week without Andre Johnson, but Matt Schaub managed to throw for 416. Yet the Texans lost to the Raiders, and the losses on the injury front were even more devastating. The Texans lost pass-rusher Mario Williams and his sack a game for the remainder of the season. Schaub suffered a banged-up shoulder and missed some practice time, but he will play Sunday. The injury list grew to 14 as the Texans head into a two-game road stretch against Baltimore and Tennessee. Johnson isn't expected to play because of his hamstring, and the Texans know it will be tough to run on the Ravens. They also know it will be a physical game. The Texans can survive a loss to the Ravens, but if they lose to the Ravens and the Titans, all of a sudden, the Titans will be atop the AFC South and might be hard to catch.

3. Greatest Show on Surf and Turf: The 1999-2000 St. Louis Rams called themselves "The Greatest Show on Turf'' when they strung out 14 consecutive games in which they scored at least 30 points. The New England Patriots, in the land of lobsters, have their own version. If they score 30 or more points against the Cowboys on Sunday in Foxborough, they will tie the Rams' mark. Stopping Tom Brady is the supreme challenge. The Cowboys rank a respectable fourth on defense in yards allowed at 291.8 a game, but this matchup figures to be a shootout between Brady and Tony Romo. The Patriots average 495.2 yards a game on offense but are giving up 433 yards. Romo may have a healthy receiving corps; Miles Austin and Dez Bryant had the bye week to heal. But the Cowboys know winning in Foxborough is tough. Since 2008, the Patriots have won 19 straight regular-season home games.

4. Great defense or bad quarterbacking:
Four of the top nine defenses are in the AFC North. The Bengals, Steelers and Ravens rank as the top three. The Cleveland Browns are ninth, allowing 320 yards a game. Most of the youngest, least experienced quarterbacks are on the AFC North schedule. The North plays the NFC West and AFC South, which features young quarterbacks Blaine Gabbert, Curtis Painter, Tarvaris Jackson, Kevin Kolb and Sam Bradford. The Bengals and Browns have young quarterbacks themselves. Sunday, Pittsburgh (playing Jacksonville), Cincinnati (Indianapolis) and Baltimore (Houston) all face AFC South teams. Gabbert and Painter don't figure to put up big numbers in these road games. Schaub goes into the Baltimore without Andre Johnson. So far, the AFC North is 4-3 against the South. If the Steelers win, they would finish their AFC South schedule with a 3-1 record.

5. Remembering Al: It will be an emotional day Sunday when the 3-2 Raiders return for their first home game since the death of Al Davis. They face the Cleveland Browns, who gave them linebacker Kamerion Wimbley for a third-round pick. Ironically, that third-round pick turned out to be Colt McCoy, who starts for the Browns. The Raiders hope to strike gold with the Aaron Curry trade, getting the fourth pick in the 2009 draft for a seventh-round pick and a conditional pick in 2013. The Raiders needed some linebacker help after losing Ricky Brown for the season. Middle linebacker Rolando McClain is also banged up and has been struggling. Quarterbacks have completed 23 passes for 256 yards against him in five games. The Raiders are the only team playing in the AFC West this week because the Broncos, Chargers and Chiefs are in bye weeks.

6. Battle for the NFC South: There are five divisional games this weekend, two of them in the NFC South. The Saints travel to Tampa, and the Falcons host the Panthers. Concern is starting to creep in for Tampa Bay and Atlanta, two double-digit winning teams from last year who are off to slow starts. After a 10-win season, the Bucs aren't as sharp on offense and defense. They are scoring 17.4 points a game and giving up 25, although those numbers are inflated by the 48 points registered by the 49ers last week. Injuries are starting to affect them. Running back LeGarrette Blount is expected to miss the game with a knee injury. The interior of the defensive line could be without defensive tackle Gerald McCoy, who has an ankle injury. In Atlanta, expect Cam Newton of the Panthers to attack the Falcons' Cover 2 defense with tight ends Jeremy Shockey and Greg Olsen. The Falcons are giving up 26 points a game. Matt Ryan's watched his offense drop off five points a game in scoring despite the addition of wide receiver Julio Jones. The Falcons are averaging only 20.8 points. To make matters worse, Jones is expected to miss the game with a hamstring injury.

7. Rex puts his foot down: Rex Ryan has denied reports that three receivers came to him to complain about the play-calling of offensive coordinator Brian Schottenheimer, but something is burning in the Jets' locker room. The Jets shipped out Derrick Mason to Houston for a seventh-round pick. Someone's got to figure out a way to get this offense going. It's struggling with the run and the pass. The good news is that Monday night's opponent is in worse shape. The Dolphins are 0-4 and coming off a bye week in which they said bye-bye to quarterback Chad Henne, who had shoulder surgery. Matt Moore starts against the Jets, who figure to get points off defense if the offense takes the day off.

8. Who's the best team in the state of New York? The Jets are 2-3. The Giants are 3-2 coming off a home loss to the Seattle Seahawks. Are the Buffalo Bills, who are 4-1, the best team in the state? We'll find out Sunday. At some point, the injuries have to catch up to the Bills. Last week, they lost wide receiver Donald Jones to a high-ankle sprain and they played without left tackle Demetrius Bell. Despite that, the Bills beat the Eagles, 31-24. The defense is worried that nose tackle Kyle Williams might not be able to play because of a foot injury. It will be interesting to see if the Bills and Chan Gailey use the no-huddle approach against the Giants. The Seahawks tired out the Giants' defenders last week with the no-huddle.

9. Fearing the 0-7 start: The Rams may be doomed. They are 0-4 coming off a bye week. Injuries have taken away their top three cornerbacks -- Ron Bartell, Jerome Murphy and Bradley Fletcher. Over the next three weeks, they face the Packers, the Cowboys and Redskins. Try stopping Aaron Rodgers, Romo and Drew Brees with fourth and fifth cornerbacks. Even worse, the Rams are adjusting poorly to Josh McDaniels' offense. The line is having trouble blocking five-step drops. Receivers aren't separating from defenders. That's leaving Sam Bradford vulnerable to hits and incompletions. The Packers, who host the Rams, must be salivating.

10. Calming down the critics: Fans in New Orleans, Green Bay, Dallas and other NFC cities can't figure out why their teams' defensive stats are so bad. Simple. Their schedules opened with hot quarterback opponents. Watch the numbers drop over the new few weeks. The Saints rank 16th in yards allowed but are giving up 25 points a game. They've faced Aaron Rodgers, Jay Cutler and Matt Schaub the last three weeks. Coming up they have Tampa Bay twice, Indianapolis and St. Louis. The Packers opened against Drew Brees, Cam Newton, Jay Cutler, Kyle Orton and Matt Ryan. They're giving up 299.8 passing yards and 22 points a game. Before their bye, they face the Rams and Vikings. Watch their numbers come down. As for the Cowboys, expect a roller-coaster ride.

John Clayton, a recipient of the Pro Football Hall of Fame's McCann Award for distinguished reporting, is a senior writer for ESPN.com.