Defensive end Brett Keisel could miss three games with a sprained medial collateral ligament. Coach Mike Tomlin also doesn't know if cornerback Deshea Townsend (hamstring, doubtful), cornerback Bryant McFadden (broken forearm, questionable) and left tackle Marvel Smith (back, status uncertain) can play.
Smith has missed six games with persistent back pain and Tomlin said Tuesday he remains "status quo." Wide receiver Santonio Holmes sat out part of the Bengals game with a concussion but is expected to play.
Parker is questionable because of left knee inflammation. He missed four games earlier because of a sprained knee and another with a shoulder injury, and the Steelers were 3-2 without him. Parker was held to 37 yards on 14 carries before his knee began bothering him again during a 27-10 victory over Cincinnati on Thursday.
The injury flare-up is occurring at the same time the Steelers' schedule is toughening, with the Patriots (7-4), Cowboys (7-4), Ravens (7-4) and Titans (10-1) upcoming the next four Sundays.
Only the Dallas game is in Pittsburgh. Only the New England game is on Tomlin's mind.
"I didn't care about the schedule in March. I don't care about the schedule now," Tomlin said. "I really don't. We play New England this week and that's where we're at. And that's where our attention needs to be. I can care less what's going to happen in the upcoming month or the subsequent weeks. That's never been our mentality and won't be."
Still, the next four games will play a role in determining playoff position and, Tomlin said, "Hey, our guys know about New England."
Losing a three-time 1,000-yard rusher like Parker for nearly half the season has affected the Steelers' ability to mount a running game to complement Ben Roethlisberger, who threw seven interceptions during home-field losses to the Giants and Colts when Parker was out.
Mewelde Moore, signed to be the third-down back, took over when Parker hurt his knee Sept. 21 against Philadelphia and averaged 101 yards in three starts. Moore has been held to 110 yards in his past four games and was stopped twice on important fourth-down runs from inside the 1-yard line against the Colts and Chargers.
The Steelers were limited to 3.3 yards per rushing attempt by Cincinnati's 24th-ranked rushing defense, with Moore getting 56 yards on 15 carries.
In and out of the lineup, Parker is only 29th in rushing with 485 yards; a season ago, he was leading the league before breaking his right leg during the Steelers' penultimate game.
"We've got to run the ball," Parker said before his knee began hurting again. "We've got to go back to playing Steelers football."
That would appear to be important to do against the Patriots, who have beaten the Steelers six of seven times over the past 10 years, counting two AFC Championship Games in Pittsburgh. New England beat them 34-13 last season, when safety Anthony Smith guaranteed a victory over the then-unbeaten Patriots.
"This week's challenges are significant," Tomlin said.
Especially if the Steelers must play with one-quarter of their lineup out. Keisel is a key not only to stopping the run but mounting a pass rush, although Nick Eason and Travis Kirschke filled in effectively when Keisel missed most of four games with a calf injury.
"Those guys have proven to us that they're capable of upholding the standard," Tomlin said. "It will be business as usual."
Tomlin also said the Steelers brought back punter Mitch Berger, who was cut nearly a month ago, partly because he is kicker Jeff Reed's holder. Berger had two sore hamstrings when he was let go, but replacement Paul Ernster averaged only 31.3 yards before being released Monday.
"When you bring in a guy like Mitch, who's got experience with it [holding], it weighs in your decision," Tomlin said. "We'll need Mitch to do a quality job punting as well."