PITTSBURGH — Maybe it's the accumulated wear and tear from all the sacks. Maybe it's his slightly separated shoulder, the bad thumb, his reduced practice time or the spotty offensive line protection. Perhaps it's all the above.

Whatever the reason, Ben Roethlisberger isn't the quarterback he was last season, or even a few weeks ago. He's certainly not the quarterback the Pittsburgh Steelers expected when they chose to pay him nearly $28 million in salary and a signing bonus this season.

Roethlisberger's problem is one more befitting a rookie than a five-year veteran who has won a Super Bowl: He keeps throwing the ball to the guys in the other shirts.

His mistakes — eight interceptions in 10 quarters — have cost the Pittsburgh Steelers (6-3) their last two home games, their once-comfortable AFC North lead over Baltimore (6-3) and maybe a bit of confidence.

Something's wrong with Big Ben, but neither the quarterback nor his team is saying exactly what it is. The numbers are telling, however: one touchdown pass and eight interceptions in his last three games, compared to nine TDs and three interceptions in his first six games.

"I am not concerned about his confidence," coach Mike Tomlin said after Roethlisberger's three interceptions proved pivotal in a 24-20 loss to Indianapolis on Sunday. "He is our quarterback because he is. If you play that position in this league, you have to remain unwavered."

Maybe unwavered isn't a word, but the Steelers are having trouble finding the right ones to describe what is wrong with their franchise quarterback. Two weeks ago, his four interceptions were the major reason they lost to the Giants 21-14 in another game they led late.

Roethlisberger's lower-grade shoulder separation has been an ongoing problem since he was hurt in the Sept. 7 opener, but not enough to prevent him from leading the Steelers to a 5-1 start. He also has a damaged ligament in his left little finger.

The achy shoulder has twice kept him from practicing until Friday of a game week, meaning he missed the two most important practices each week.

"I don't think it's that big of an issue," Roethlisberger said of the reduced practice time. "I'm taking mental notes and I'm seeing everything that is going on, so it's not as tough as it may seem."

The falloff in Roethlisberger's play is a worry, especially with the Steelers readying to play two home games in five days, on Sunday against the Chargers (4-5) and a week from Thursday against the Bengals (1-8).

Roethlisberger's slippage is evident. He has been sacked the third-most times of any NFL quarterback (28) and he is tied for second with 11 interceptions, or as many as he had last season. His 76.1 passer rating ranks only 25th — he trails Dan Orlovsky and Tyler Thigpen, among others — and is far below his 104.1 of last season.

There was nothing wrong with his 71.4 percent throwing accuracy against Indianapolis, but what ruined his day was his 7.1 completion percentage to the Colts.

His first interception came with the Steelers trying to sit on a 10-point lead and led to a game-changing score by the Colts with six seconds left before halftime. The second set up Indianapolis' go-ahead touchdown late in the fourth quarter. The third, thrown into the Colts' end zone, ended the game.

"When you feel like it's your fault, it really hurts," said Roethlisberger, who said his discomfort was more emotional than physical.

None of his teammates would guess afterward how much the bad shoulder is affecting Roethlisberger's play. The Steelers were coming off a dominating 23-6 win at Washington six days before, but Byron Leftwich — not Roethlisberger — directed the two key TD drives in that second half.

With only three days off between their next two games, the Steelers won't have much recovery time given their fast-growing injury list that includes running back Willie Parker (shoulder), linebacker LaMarr Woodley (calf), cornerbacks Deshea Townsend (hamstring) and Bryant McFadden (broken forearm), left tackle Marvel Smith (back) and, yes, Roethlisberger.

Parker's shoulder injury appears to be worse than originally thought — the Steelers aren't saying if he has a torn labrum — but Tomlin said he could play against San Diego.

A bigger concern now might be how Roethlisberger will play.

"It's frustrating because you feel like you played well, and there's a turnover at the end of the half and the turnover at the end," he said. "I take it on myself. I let the guys down, offense and defense, but the good thing is it's not the end of the season. We'll come back."