PITTSBURGH - As the career of the NFL's No. 5 all-time rusher winds down, Pittsburgh Steelers running back Jerome Bettis will never be known as Mr. September.

The Steelers held back Bettis early on the last two seasons, mostly because he wasn't needed then for his usual 20-25 carries a game. But as the season moves on and big games need to be won, Bettis has become football's version of baseball's closer: He comes in at the end to secure victories.

Bettis, playing for the first time since last season's playoffs, came off the bench during Monday night's 24-22 victory in San Diego to carry 17 times for 54 yards and a touchdown. During the decisive drive in which quarterback Ben Roethlisberger injured a knee, Bettis carried on seven of the 10 plays leading to Jeff Reed's winning 40-yard field goal with six seconds remaining.

"They knew I was going to get the ball - they had nine in the box," the 255-pound Bettis said, referring to the Chargers committing nine defenders to stopping the run. "But I was fortunate enough to make a guy miss, or to take a guy with me. That's why I'm still around."

A preseason calf injury kept Bettis out of the first three games. And when Willie Parker rushed for 272 yards in the first two games, it seemed unlikely the 33-year-old Bettis would have played much even if he was healthy.

After a string of seasons in which Bettis piled up big yardage only to get hurt before or during the playoffs - it happened in 1996, 2001 and 2002 - the Steelers began limiting his early seasons carries. The last two seasons, he has only 12 carries for 13 yards in September.

But in the 11 games dating to midseason 2004 in which he has 10 or more carries, Bettis has 1,089 yards rushing and a 98-yards-per-game average. Despite being limited to six starts last season, Bettis missed a ninth 1,000-yard season by only 59 yards.

That's why Bettis got agitated when his role was questioned following Parker's big start. With 2004 starter Duce Staley returning following training camp knee surgery, it wasn't certain how Bettis fit into a crowded backfield.

"I'm fifth all-time, and I fit in somewhere," Bettis said. "It was like, wait a minute, I'm not just an ordinary guy. I've been able to do some extraordinary things in an ordinary body, but I'm not an ordinary guy."

Now, Bettis' role figures to expand, just as it did a year ago when he had six 100-yard games in as many starts.

"Jerome Bettis, he gives you something," coach Bill Cowher said. "He's a very special back."

Bettis weighed retiring after the Steelers lost to New England in the AFC title game in January, but returned to take at least one more run at a Super Bowl. The game will be played in his native Detroit, and Bettis didn't want to miss out on playing there if the Steelers make it.

Because Bettis and Staley get along well - Bettis didn't complain when Staley started the first half of last season - the Steelers have avoided the locker room conflicts other teams might have while figuring out how to get one football to three backs.

"Wherever I can fit in and contribute, I'll be happy," Staley said.

Now, it seems that it will be Staley's role that is limited, not Bettis'. Cowher revealed this week that Staley may not be 100 percent all season because of the knee operation, and that means he may not get many carries unless Parker or Bettis gets hurt.

For now, Parker will start and Bettis will finish, just as Bettis has done consistently while rushing for 13,348 yards in 13 seasons.

"It's working that way, and, hopefully, if I can stay healthy toward the end of the year, it's a big plus for us," Bettis said. "That's the fun part, to be able to go out there and still contribute. To be on the sideline all those weeks, it was frustrating, so it was good to go back out there and pound the ball and show people it was still there."