Dan Pompei

We will get our final clue this week to one of the great mysteries of the 2008 season — the San Diego Chargers. But we still probably won’t be able to figure out this team.

Were they the team we thought they were before the season? The team they became for most of the season? The team that is finishing with a flurry and beating opponents by an average of 15 points per game in December?

There are as many whys about the Chargers as grains of sand on Mission Beach.

• Why doesn’t LaDainian Tomlinson look like himself?
• Why can’t the offensive line clear holes the way it used to?
• Why aren’t they sacking the quarterback more?
• Why isn’t Antonio Gates producing like he has in the past?

Why, why, why?

"They are a very talented football team, but there is something wrong there," said one defensive coordinator whose team played the Chargers. "You can’t put your finger on it, but they are big time underachievers. They come on the field and scare the heck out of you, big, strong, athletic and fast, but something is missing. They display a lot of arrogance during their warm-ups, constantly talking to the other team, after the kick-off the talk stops and they look average at times."

The most puzzling aspect of the Chargers may be their running game. They are averaging 3.8 yards per carry compared to 4.2 a year ago, and 95.8 yards per game compared to 127.4 a year ago.

Among the reasons: they miss Michael Turner; they haven’t been ahead in games often so they haven’t had as many fourth-quarter rushing opportunities; and Tomlinson seems to be missing something.

His critics say that at 29 and in his eighth NFL season, he is showing signs of age. Tomlinson does have high mileage with 2,643 rushes and 11,664 yards. In the history of pro football, only 15 backs have more rushing attempts than Tomlinson, and only 13 have more yards.

But don’t be surprised if Tomlinson finishes strong and bounces back next season. "Tomlinson is the real deal, but he is playing hurt and he is not 100 percent," the defensive coordinator said. "There are plays that I’ve seen where he has a chance to take it all the way and yet he is tackled for three or four yards. It looks to me like the toe he injured early in the year is still bothering him, yet he keeps playing and not complaining about it."

Special feature NFL power rankings: Who's the 1? Make your own rankings, compare them to NBC Sports crews NBCSports.com

The Chargers season began to unravel when they lost linebacker Shawne Merriman for the season. The defense also lost its identity early on. But since Ron Rivera was promoted to defensive coordinator at the bye, the defense has looked more like what we expected.

In the first eight games, the defense allowed 24.8 points and 371.6 yards per game. In the last seven under Rivera, it has allowed 18.1 and 317.1.

After having 11 takeaways in their first 11 games, the Chargers have 11 in their last four.

So clearly something good is happening on defense, even with Merriman on the sideline.

It may be cliché, but this is a team that opponents would not want to play in the postseason. Philip Rivers is in the midst of a fine season at quarterback. His passer rating of 104 is best in the league. His offensive surrounding cast has as much talent as any team they could oppose. And the defense has found its mojo.

As disappointing a season it has been in San Diego, it isn’t too late for the Chargers. They just have to start walking like they’ve been talking.