The Tennessee Titans vs. the Buffalo Bills — or maybe the Baltimore Ravens — for the AFC title?

At the beginning of the season, it was assumed by nearly all prognosticators — and rightly so, I think — that the AFC had the three best teams in the NFL, the Giants’ colossal upset win in the Super Bowl notwithstanding.

As it turns out, New England’s defense is probably too old to win for them even if Tom Brady hadn’t been injured. The Indianapolis Colts, with what looked like a clear path to the Big Game, suddenly don’t know how to hold onto a lead with 25 seconds left to play. And as for the San Diego Chargers, who were probably the best team in the league over the second half of the last regular season, they went from scoring 48 points against the Jets one week to being held to less than 30 by the Oakland Raiders in the next.

It’s too early to count any of these three out, but while they’re making up their minds about whether or not they want to play in the postseason, the Titans are racking up the wins and making history — well, Tennessee Titans history at least. After beating a mediocre Minnesota Vikings team 30-17 yesterday, the Titans are 4-0 for the first time in franchise history (and yes, that includes when they were the Houston Oilers).

Tennessee’s improbable start has been pretty much ignored by the sports press for two main reasons: The first is that the team hasn’t been led, as anticipated, by the fabulously talented quarterback Vince Young, and the second is that the team is instead being led by a proven mediocrity, Kerry Collins.

Young injured his left knee in the first game of the season and “disappeared” the day after the game, where fans booed him after his second interception, resulting in Tennessee coach Jeff Fisher calling the police. As if that weren’t bizarre enough, there were rumors he was talking of suicide. I don’t know how true that was, but if I was a professional quarterback and I lost my job to Kerry Collins, I think I’d consider killing myself, too. (In truth, last year was Young’s second in the pros and he seems to have learned nothing about reading pass coverages; Collins was actually better than Young coming off the bench.)

Collins is 35 and has thrown just three more TD passes (176) than interceptions in his 14-year career. He really hasn’t been terrible this season (a respectable 7.0 yards per throw average) and he wasn’t bad in the win over the Vikings — mostly he helped his team by not fumbling any snaps from center or throwing any interceptions.

But how, then, are the Titans winning?

On defense, that’s how, and right now it just might be the best in the NFL. Paced by their terrific defensive lineman, Albert Haynesworth, and a defensive back whose name seems to have been borrowed from a J.P. Donleavy novel, Cortland Finnegan, the Titans turned in a typical Tennessee defensive performance yesterday, holding Minnesota to 253 yards passing and only 80 rushing while forcing four turnovers, three of them fumbles. Finnegan had six tackles and knocked down two passes while Haynesworth, who was probably the best defensive lineman in the league last year, had six solo tackles and two sacks on Vikings passer Gus Frerotte.

The only problem is that the Titans had just 275 total yards themselves, 199 passing and 76 on the ground. On days when your defense forces three fumbles, you can get away with offensive stats like that. But recovering fumbles is pretty much a 50-50 proposition and can’t be counted on week in and week out. I don’t think the Titans are for real, or at least I can’t see them winning the conference unless Young develops into a first-rate passer. We’ll know more about the Titans next week when they play the Baltimore Ravens (who play the Pittsburgh Steelers tonight).

Meanwhile, there are reports that Young has been healing both physically and mentally. Vince, here’s my advice: Keep some ice on the knee, read “The Myth of Sisyphus,” and study some NFL pass coverages.

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If I had to put my money on an upstart AFC team this year, it would be the Buffalo Bills, who, if anything, are even more colorless and anonymous than the Titans. Of course, the way to get noticed in the NFL is to win, and, amazingly, that’s what the Bills have done in their first four games. Two of those wins came against Jacksonville and Oakland by a total of just five points, but as any Bills fan will tell you, it beats the heck out of losing.

Football analysts are saying that the Bills have the most promising core of young talent in the league, including quarterback Trent Edwards, who was awful near the end of last season, but after beating the St. Louis Rams 31-14 yesterday has now passed for 930 yards and an excellent average per throw of 9.8. That talent evaluation also includes wide receiver Lee Evans who, at age 27, seems to be hitting his stride with a career average of 15 yards a reception, including his 49-yarder for a touchdown against St. Louis, which brings his YPA this year to an eye-opening 23.7. Evans is the secondary-stretching threat Buffalo has been looking for since Andre Reed was at his peak.

Due to another of the NFL’s really strange scheduling quirks, New York’s only true home team won’t meet the Jets till Week 9, at Buffalo. They play again in Week 15 at the Meadowlands. Incredible as it seemed at the beginning of the season, those two games could well decide the AFC East — and the Jets just might have to win both.

Mr. Barra’s next book is “Yogi Berra, Eternal Yankee,” due out in March 2009 from W.W. Norton.