Five nuggets of knowledge about Week 4:
49ers' defense in focus: The San Francisco 49ers brought the NFL's best defense into the 2012 season. That was the widely accepted assumption, anyway. But after Christian Ponder and the Minnesota Vikings scored a 24-13 victory against the 49ers in Week 3, San Francisco could stand to reverse a few early statistical trends. The 49ers are even in turnover differential, collecting and committing four. They were plus-28 last season. The 2012 team also has allowed five touchdowns on five red zone possessions. The 49ers allowed 14 in 34 possessions last season. Their Week 4 opponent, the New York Jets, led the NFL in red zone TD percentage last season. The Jets are off to a slower start this season, ranking just 24th.
Cardinals, Seahawks tighten screws: Arizona and Seattle have had the best defenses in the division to this point in the season. Neither has allowed more than 20 points in a game despite facing Tony Romo, Aaron Rodgers, Michael Vick and Tom Brady. Arizona is the only NFL team to hold every opponent beneath 20 points. The Cardinals, Seahawks and unbeaten Atlanta Falcons are the only teams to allow fewer than 50 points through three games.
Rams in no rush: The St. Louis Rams promoted a run-first mentality when Jeff Fisher arrived as coach. Fisher's current team (Rams) and former team (Titans) are the only ones without a rushing TD through three games. The Rams have scored all four of their offensive TDs through the air. They now face a Seattle defense allowing 2.5 yards per carry to opposing running backs. That includes a 0.4-yard average in the red zone, where running backs average 2.6 yards per rush across the NFL. Opposing backs have eight rushes for 3 yards and two TDs in the red zone against Seattle.
Sending a message: The Rams have a 12-41 (.226) nondivision record since 2007. They are only 4-26 (.133) against NFC West opponents in the same period. Fisher must stop the divisional bleeding for the Rams to make significant progress this season. His first opportunities come with Seattle and Arizona visiting the Edward Jones Dome in a five-day period that begins Sunday. The Rams are 2-18 against those teams since 1997. That includes 1-4 at home against the Seahawks and 0-5 at home against the Cardinals.
Upping those playoff odds: The NFC West could have three teams at 3-1 or better heading into Week 5. That seems to be what oddsmakers expect to happen. Arizona (3-0) is roughly a six-point favorite at home against the Dolphins. San Francisco is roughly a 4.5-point favorite against the Jets. Seattle is roughly a three-point favorite against the Rams.
Cardinals fans should know that teams starting 4-0 have earned playoff berths 82.5 percent of the time (52 of 63) under the current postseason format. The percentage is 64.8 (118 of 182) for teams starting 3-1, 35.3 percent (71 of 201) for teams starting 2-2 and 14.7 percent for teams starting 1-3 (22 of 150). Of course, those percentages fall for teams playing in divisions with multiple playoff contenders.
Note: ESPN Stats & Information contributed to this item.