Steve Silverman

Why has Superman suddenly turned into a mere mortal?

That’s the question San Diego Chargers fans are asking as the NFL's stretch run approaches. What happened to LaDainian Tomlinson?

Tomlinson appears ordinary for the first time of his career. Entering Sunday’s game against the Colts, Tomlinson has rushed for just 686 yards and 5 touchdowns. He is averaging 3.8 yards per carry, the lowest since his rookie season.

In addition to that major dive in his production — he had 1,815 yards and 28 rushing TDs in 2006 — Tomlinson is no longer the exuberant and ultraconfident back that he had been throughout his previous seven years. He no longer has bounding energy or the eye-popping ability to run through tackles and outrace the defense.

The dip in production is a problem for the underachieving Chargers (4-6), but Tomlinson's downcast attitude may be more revealing. The bumps, bruises and nagging injuries may be catching up with a back who usually accounted for more than 400 touches a season. His 182 rushing attempts through 10 games would keep him below 300 carries for the first time in his career. He's on pace to rush for 1,098 yards, by far the lowest total of his career.

Part of the blame lies with Chargers’ offensive and defensive lines.

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

The offensive line isn't opening up the same holes and doesn't get off the ball with as much quickness or precision as last year. The defensive line isn't forcing any turnovers or limiting opponents, which takes away opportunities from the San Diego offense.

The slowdown may have started in last year’s postseason. Tomlinson hyperextended his knee during an AFC divisional playoff win against the Colts. As a result, he had just two carries in the AFC Championship.

Fast forward San Diego's opener. Tomlinson jammed his right big toe on the Chargers’ final drive, and re-injured it in Week 2 against Denver. While Tomlinson has not missed any games this season, the injury took away his dynamic latertal ability.

After an 11-10 loss to Pittsburgh on Sunday, Tomlinson expressed disappointment with his team's struggles, his own performance (18 carries for 57 yards) and even indicated that the end of his career was within sight.

“Each year is another season gone and I’ll be the first to tell you that I am running out of time,” Tomlinson said this week. “I don’t know how many more years I’m going to play, but at this point you just hope for the best. That is all I can really say about it. You just hope that things, if they don’t turn out the way they should this year or if we don’t make it into the playoffs, you question what’s next and that’s just where I am right now.”

The combination of nagging injuries and downbeat attitude show that even an elite NFL player can't resist the league's rigors. It's the inevitability that comes as every player realizes that he can’t play forever and will slow down a little bit as time goes by.

Tomlinson’s inability to return to the lineup against the Colts in last year’s playoff game took many of his teammates by surprise. It may have been the first time in his career that his body did not respond the way he wanted it to. This season has merely reinforced it.

Tomlinson remains one of the main keys to the Chargers offense. He is without peer as a runner, receiver and as a blocker when healthy.

But he also needs to change his perspective. All running backs do so when they realize their skills are eroding. The sooner Tomlinson adjusts, the better it will be for the Chargers and his career.

Also on NBCSports.com Beyond the Arc: No. 11 Mich. St. takes big step forward Chandler: Jeremy Lin was special even in 8th grade What NFC teams need this offseason  |  And AFC DeMarco: Dodgers could become a contender Follow us on Twitter: @NBCSports  |  And Facebook