Is another QB's streak in jeopardy?

Brett Favre's consecutive-games streak ended last week. Could Peyton Manning's streak of eight consecutive playoff seasons end Sunday?

Week 15 might be the most dramatic and important week of the season. A few weeks ago, many of the playoff contenders separated themselves from the pretenders in this season of parity. This weekend could be a time of closure for some of the playoff spots.

The Jacksonville Jaguars could clinch their first AFC South title if they beat the Colts on Sunday at Lucas Oil Stadium. The Pittsburgh Steelers can clinch a playoff spot if they beat the New York Jets. The Chicago Bears could win the NFC North if they beat the Favre-less Minnesota Vikings on Monday night. The Atlanta Falcons can lock up a playoff spot with a win in Seattle.
The New England Patriots have already qualified for a playoff spot. The Baltimore Ravens, New York Jets, New Orleans Saints and New York Giants have scenarios in which they could get their playoff berths this weekend, but their fates might be better determined in Week 16. (Here are playoff-clinching scenarios for Week 15.)

1. Peyton Manning's back is against the wall: Manning treats every offensive possession as though he's in the fourth quarter of a Super Bowl. Normally, he's accustomed to playing his last meaningful regular-season game in Week 15, because the Colts, who won 12 or more games a season from 2002 to 2009, usually rest starters once their playoff seeds are locked in. Manning and the Colts could be in the rare position of playing two meaningless games if they lose the division to the Jaguars on Sunday. Two things are certain: The Colts are favored because Manning is 18-2 in AFC South home games since 2005, and the game should be close. The past six meetings between these teams have been determined by seven points or fewer. The Jaguars' strategy is to win the time-of-possession battle by letting Maurice Jones-Drew run through the Colts' defense. Colts coach Jim Caldwell must come up with some kind of pressure package against the Jaguars. They can't just play Cover 2, so a safety either has to rush or play near the line of scrimmage. According to ESPN Stats & Information, in the past two meetings, Jaguars quarterback David Garrard completed 62.3 percent of his passes, threw for three touchdowns and had a 94.2 quarterback rating against the Colts when they rushed four or fewer players. When the Colts rushed five or more, Garrard completed 55.2 percent of his throws and had a 79.7 rating.

2. Cool Brees blowing into Baltimore: Drew Brees played his college ball at Purdue, but his pro career has been played in balmy San Diego and in the comforts of the Superdome. With the East Coast in freeze mode, Brees heads to Baltimore with some warm experiences in cold-weather games. He usually only gets one cold game a season, but he warms to the conditions. Two weeks ago in Cincinnati, Brees was 24-for-29 for 313 yards and two touchdowns. In December 2009, he was 35-for-49 for 419 yards against the Washington Redskins. But those games were against inferior competition. Two years ago, Brees lost a 27-24 road game in chilly Chicago. He completed 24 of 43 passes for 232 yards and was sacked six times. The Ravens' defense will bring the heat, particularly after its embarrassing second-half performance Monday night against the Texans. Baltimore's secondary was helpless and tired trying to stop Matt Schaub in the second half. The Ravens have lost eight fourth-quarter leads this season.

3. Will the Giants bring back the Vick Blitz? The Eagles beat the Giants 27-17 on Nov. 21, but New York's defense came up with novel ways of making Eagles quarterback Michael Vick uncomfortable. It blitzed an extra defensive back most of the time, often trying to force the left-handed quarterback to go to his right, where it's more difficult for him to set his feet and throw. Those blitzes kept Vick in the pocket. He has become a dangerous passer from the pocket, but no quarterback can do well when he's pressured in the pocket. According to ESPN Stats & Information, the Giants kept Vick in the pocket for 83 percent of his 47 dropbacks. That strategy also affected him outside the pocket. He didn't run for a first down on his six scrambles outside the pocket, according to Stats & Info. The pressure and the hits have taken a toll on Vick's body and his performance. Stats has charted Vick as being under duress or being hit on 50 pass attempts this season. In his first four games, he completed 56 percent of his passes and had an 89.9 quarterback rating while under duress. In the past six, he's completed only 20 percent and has a 22.9 rating on those challenged throws.

4. Jets falling: A year ago, the Jets sneaked into the playoffs with wins against the Colts and Bengals when those playoff teams were resting their minds and starters in preparation for the playoffs. This season, the Jets (9-4) could be back in the playoffs only because of their fast start. Things are falling apart for New York. The ground-and-pound running attack is missing. Shonn Greene is averaging only 3.6 yards a carry over the past month, and LaDainian Tomlinson hasn't done better than a 57-yard rushing day since the fifth week of the season. Mark Sanchez is struggling with his confidence and was almost benched last week. The defense is having trouble getting pressure on quarterbacks when teams go to two-tight end sets or maximum blocking schemes. The Jets lost their strength coach, Sal Alosi, who was suspended indefinitely for tripping a Dolphins gunner on a punt. On Sunday, the Jets play the Steelers, and next week they travel to Chicago to play the Bears. The Steelers should be able to take away the run, because that's what they do best. That will force Sanchez to try to win the game against Steelers blitzes.

5. Two playoff teams in the "Show Me" State? The Kansas City Chiefs entered the season figuring they were a six-win team that might win eight or more if they got a few breaks. They are 8-5 and lead the AFC West. The Rams thought they were a four-win team that might get a few breaks to get six wins. The Rams are tied for the lead in the NFC West. The lesson learned by both franchises is the value of a quarterback who is functioning at a high level. The Rams vaulted to six wins with Sam Bradford, the odds-on favorite to win offensive rookie of the year honors. He has passed for 2,884 yards and will join Manning and Matt Ryan as the only rookie quarterbacks to throw for more than 3,000 yards. With offensive playmakers who can make plays after the catch this season, Chiefs quarterback Matt Cassel has gone from a quarterback who threw a touchdown and an interception a game last season to one this season who has 23 touchdown passes and only four interceptions. Cassel missed last Sunday's game against the Chargers because of an appendectomy, and the Chiefs were shut out with Brodie Croyle behind center. Cassel returned to practice this week.

6. Sunday night downer: NBC eagerly looked forward to the Week 15 Sunday night showdown between the Green Bay Packers and New England Patriots. A Tom Brady-Aaron Rodgers matchup could have been a classic. NBC needs to have Bob Costas teach Rodgers how to slide. On an 18-yard scramble last Sunday, Rodgers suffered his second concussion of the season as he was hit by a couple of defenders as he was going to the ground. He has been ruled out for Sunday and will be replaced by Matt Flynn, who couldn't do anything with the Packers' offense in a 7-3 loss to Detroit. Patriots' blowout, anyone? The second half could be a showdown between Flynn and Patriots backup Brian Hoyer, after Brady puts up a nice first-half lead.

7. Andre Johnson-Cortland Finnegan, Round 2: Three weeks ago, Texans receiver Johnson grew tired of constant jabs by Titans cornerback Finnegan, and the best fight of the year broke out. Each player was fined $25,000. Those attending Sunday's game in Nashville will get the rematch, which could be the most interesting part of this game. Despite a nagging ankle injury, Johnson is having his usual Pro Bowl season, with 80 catches for 1,158 yards and seven touchdowns. Finnegan has been overly busy this season. Receivers have grabbed 52 of 84 passes thrown on him for 698 yards. He's the fourth-most-targeted defender in football. "Retaliation is for the birds," Finnegan told reporters Wednesday. The game itself means little for the teams but a lot for the coaches. Jeff Fisher of the Titans and Gary Kubiak of the Texans are 5-8, and their futures with their teams will be reviewed at the end of the season.

8. NFC South symbol: The NFC South may have the Falcons as a member, but the official bird for the South should be a vulture. The NFC South has feasted on the NFC West this season with a 10-3 record. The Bucs, Saints and Falcons have combined to go 9-1 against NFC West roadkill. The Falcons go cross-country to face the 6-7 Seahawks. The Panthers have a home game against the Arizona Cardinals. The Falcons definitely can't afford to lose the Seahawks game, because wins against the Seahawks this week and the Panthers in Week 17 guarantee they will win the division. The Panthers may not want to win the Cardinals game because it could cost them the top pick in the draft and the chance to select Andrew Luck if he turns pro. The Bucs are the ultimate NFC South vultures. They host the Detroit Lions on Sunday, and if they beat the Lions and the Seahawks in Week 16, they will be 10-0 against teams with losing records.

9. Too many interims: Jerry Jones wanted to host a Super Bowl in his new stadium, but he has an interim coach (Jason Garrett) and a 38-year-old interim quarterback (Jon Kitna). The Vikings have an interim coach (Leslie Frazier) and need an interim stadium now that the Metrodome is closed because of a deflated roof. The Broncos have an interim coach (Eric Studesville) and an interim starting lineup, thanks to numerous roster blunders. The NFL stands for "Not For Long," and the only thing good about the Cowboys', Vikings' and Broncos' seasons is that they are over in three weeks. The Cowboys host the Redskins. To play the Bears on Monday night, the Vikings need not only a new home but a new quarterback to replace Brett Favre, who won't play because of an injured right arm. With Tarvaris Jackson on injured reserve with a turf toe injury, the Vikings will start rookie Joe Webb or Patrick Ramsey, who was signed Wednesday. The Broncos visit the Raiders, who routed Denver in their first meeting this season, 59-14. The big news? Tim Tebow will make his first start for the Broncos.

10. Bottom Feeders: The most interesting part of these three games -- Arizona-Carolina, Cleveland-Cincinnati and Buffalo-Miami -- is the return of rookie quarterback Colt McCoy to the Browns' starting lineup. McCoy was 2-3 before suffering a high ankle sprain, but he completed 63.8 percent of his passes and averaged 22.8 points a game in his starts. If McCoy beats Carson Palmer, it may force the Bengals to look at Luck at quarterback in the draft if they get the first pick. The Cardinals-Panthers game features two rookie quarterbacks -- John Skelton of the Cardinals and Jimmy Clausen of the Panthers. Six rookie quarterbacks have started this season. The Dolphins can keep their faint playoff hopes alive if they can win a home game against the 3-10 Bills.

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