PITTSBURGH - They played most of Sunday's game with a special teams player at linebacker, a tight end at fullback, an undrafted former backup at nose tackle and, yes, that rookie quarterback who wasn't supposed to play this season.

The Pittsburgh Steelers (8-1) already were one of the NFL's biggest surprise stories, with a seven-game winning streak and consecutive upsets of the Patriots and Eagles. Now they're surprising even themselves with their unexpected depth and ability to withstand potentially lineup-wrecking injuries.

Maybe it's because they are taking a cue from a visibly driven Bill Cowher, who has taken a team coming off a 6-10 season and helped shape it into, alongside New England and Philadelphia, one of the NFL's three best teams so far this season

One of the most visible examples is Jerome Bettis, who has rushed for 252 yards over the last two weeks while filling in for the injured Duce Staley. Through six games, Bettis was averaging fewer than 2 yards per carry and, seemingly on his last legs, the NFL's No. 6 career rusher was being used almost exclusively in short-yardage situations.

"That's what I'm here for - to be a relief pitcher, so to speak," Bettis said after running for 103 yards in a 24-10 victory Sunday in Cleveland. "I am just doing my part. This team is special. We have interchangeable parts, where if someone is not able to go, the guy behinds him steps up."

Still, the Steelers couldn't possibly have expected to be 8-1 for only the fourth time in franchise history - they also were in 1973, 1975 and 1978 - with so many key players missing:

Right guard Kendall Simmons, enjoying perhaps the best training camp of any Steelers lineman, was lost for the season to a knee injury during camp. But replacement Keydrick Vincent has played so well, it's almost as if Simmons wasn't gone.

Casey Hampton, a Pro Bowl nose tackle and the key to the Steelers' run defense, also went down with a season-ending knee injury, on Oct. 17. But since undrafted free agent Chris Hoke replaced him, the Steelers' last three opponents - including the previously unbeaten Patriots and Eagles - have averaged only 32 yards rushing.

"This team has been very resilient and players are stepping in," Cowher said.

Cornerback Chad Scott (quadriceps) was lost for six weeks Oct. 17, but 13-year NFL veteran Willie Williams has been more than an adequate replacement despite not starting a game in 2002 or 2003 for Seattle.

The Steelers were forced to use James Harrison at outside linebacker when Joey Porter was ejected before Sunday's game. The Steelers wouldn't have deactivated Porter's backup, Alonzo Jackson, if they had known Porter couldn't play, yet Harrison - mostly a special teams player - made the tackle on two of the first three plays and had his first NFL sack.

Backup tight end Matt Cushing filled in at fullback after starter Dan Kreider was injured on the opening series and didn't return Sunday.

Larry Foote, a career backup, was more than a fill-in when former NFL Defensive Rookie of the Year Kendrell Bell missed seven games with two separate injuries. Foote is the team's fourth-leading tackler and has three sacks.

Then there's Ben Roethlisberger, the first NFL rookie quarterback of the Super Bowl era to win his first seven starts. He might not be playing if Tommy Maddox hadn't injured his right elbow Sept. 19.

With players such as Hoke, Foote, Vincent - and, yes, Roethlisberger - so eager to play for the first time in their NFL careers, it might explain why the Steelers have avoided a letdown as they begin looking to Sunday's game in Cincinnati (4-5).

"We are not that much better," Cowher said. "If you start to take yourself too seriously, that is the trap you can fall into. We are not going to do that. It takes everyone on this team."