The AFC South began the season promising two veteran Super Bowl contenders and two young teams with breakout potential. Three of these teams have kept up their side of the bargain, but in Music City they’re humming the Crumbling Steve McNair Blues.

INDIANAPOLIS COLTS (6-3)

For the 14 remaining Americans who have not yet heard, Peyton Manning is having a great season. With 31 passing touchdowns, he has already surpassed his total from last season and is on pace to top Dan Marino’s all-time record of 48. He also throws less than one interception per game. As far as the Colts winning a title, this means nothing. Manning’s greatness will once again end in failure if the Colts defense cannot improve significantly over the next seven weeks.

It may look like the Colts defense is trending towards better performance because of last week’s 49-14 trampling of Houston. But that was just one game.

Looking at the Colts on a week-by-week basis shows a relatively straight line of poor defense, with two big blips: the Houston win, and a 35-14 win over Oakland in Week 5. In both games, the Colts had three interceptions. In no other game have they had more than one, and in no other game has their defense been above average. The offensive recipe against Indianapolis is obvious: Double-team pass rusher Dwight Freeney and scoring against the Colts becomes much easier.

Even a playoff spot is not assured, as Indianapolis is locked in a tight race with Jacksonville to win the division. The Colts must be cursing the NFL schedule makers, who inexplicably decided to send them on the road twice in five days. Chicago and Detroit should be teams the Colts beat easily, but there’s a good chance that with only four days to prepare, they could lose to an inferior Lions squad on Thanksgiving. A loss there may mean the difference between the division and a wild card, or even worse, between a wild card and a January tee time.

JACKSONVILLE JAGUARS (6-3)

Every year, one NFL team wins far more games than its statistics would otherwise indicate. Last year, that team was Carolina; this year it is Jacksonville. Every single Jacksonville win has been by six points or less, and not once this season have they risen into the top half of the Football Outsiders ratings.

The Jaguars pose a dilemma to objective analysis. Can their record be attributed to “clutch performance” and “an ability to just win?” Or is this just a mediocre team with more than its share of lucky breaks? In an NFL season that lasts only 16 games, there’s a significant chance that an average team may finish 10-6, or 6-10. NFL analysis must accept the fact that even the most accurate advanced metrics match wins and losses far less often than in other sports.

Even if you get the lucky breaks that open the door to a close victory, you need a quarterback with the maturity to lead that game-ending drive, and quarterback Byron Leftwich has been unflappable in his second year as the starter. Leftwich’s recent injury worried Jaguars fans, but David Gerrard is one of the best backups in the NFL.

On the other side of the ball, Jacksonville’s strength is stopping the run. Defensive tackle Marcus Stroud gets much of the credit, but the players be hind Stroud – middle linebacker Mike Peterson and run-stuffing safety Donovin Darius – may be even better.

Jacksonville would be happy to follow the script written by the 2003 Panthers, but the complicated AFC playoff picture means they may not even make the postseason. If they do, beating the Steelers and Patriots will require improved play as well as clutch performance.

HOUSTON TEXANS (4-5)

With four wins in five games, Houston looked like it was finally shedding its expansion cocoon to take off as a playoff bound butterfly. But losing their last two games by a combined score of 80-27 has crippled their playoff dreams.

But even a 7-9 season would qualify as a positive development for this franchise, especially because of signals that its young stars have finally matured. Before last week’s unexpected stumble against the Colts, quarterback David Carr led the Houston passing offense into the league’s Top 10.

Andre Johnson has become a force at wide receiver, catching highlight passes and forcing defenses to concentrate coverage on him. That opens up the field for Houston’s other receivers, Jabar Gaffney and Derick Armstrong, and they have made plenty of highlight reels as well.

Houston hoped to be building a set of “triplets” to rival the famous Aikman-Smith-Irvin combination in Dallas, but the running back role must be recast. Domanick Davis’s 4.3 yards per carry average of a year ago has dropped to an abysmal 3.0 yards per carry, with the nadir of his season being his 10 yards on 12 carries against the porous Chiefs’ defense.

Houston’s defense is maturing as well. It was among the NFL’s worst early in the season but has played its three best games of the season over the past four weeks (Houston is the only team to intercept Peyton Manning twice) and now ranks as above average.

Does this defensive improvement imply a return to the playoff race over the final seven weeks? Probably not, especially since the Texans have the hardest remaining schedule in this division. But Houston is set up nicely for a strong 2005, and is an early contender for the role of “suddenly dominant team,” played this season by the Steelers.

TENNESSEE TITANS (3-6)

At the end of last season, the Titans could make a case that they were the best team in football, kept from the Super Bowl because they had to travel to Foxboro instead of hosting the Patriots in Nashville. This season, that great Titans team has disintegrated.

Some decline was expected from the defense, which faced a number of preseason injuries and lost veterans Javon Kearse and Robaire Smith to free agency. But with the exception of a Week 4 fiasco against San Diego, the Titans pass defense has been just as good as last season. Run defense has been poor, but that’s not as big a drop as people think. Last year’s title of “best run defense in the NFL” was a mirage based on the fact that the Titans faced the fewest rushing attempts in the league.

The deterioration of the offense has been far worse and far more surprising. Quarterback Steve McNair was the league’s co-MVP last season, due almost as much to his incredible ability to play through pain as to his success. Though he has always taken more physical abuse than the average quarterback, there was no reason to expect this season to be the one in which McNair suddenly reached the breaking point.

In fact, McNair was going to get his first chance in years to run a balanced offense with an improved running game, as the Titans replaced broken-down veteran Eddie George with young halfback Chris Brown.

But with the exception of one game, a Monday Night contest against Green Bay, McNair has been a black hole of offense in 2004. Our metrics say that only Craig Krenzel, Jay Fiedler, and Ken Dorsey have subtracted more value from their teams’ offenses than has McNair. The Titans have actually played better since he sat down to rest his injuries and backup Billy Volek took over.

Tennessee will probably be better in the second half, but not by much. Why McNair finally collapsed is a mystery, but the bigger question for the Titans is whether he can rebound in 2005. If he can’t, Tennessee will need to find a new starting quarterback for the first time since they moved to Nashville in 1997.

Mr. Schatz is the editor in chief of FootballOutsiders.com.