Polamalu is expected to practice on a limited basis Wednesday for the first time since tearing the medial collateral ligament in his left knee Sept. 10 against Tennessee -- an injury that potentially could have sidelined him until midseason.
Polamalu, a five-time Pro Bowl player, will wear a brace on the knee. He must show the Steelers' medical staff that he can stop and start and change directions before he plays again, but he has not been ruled out of Sunday's game at Detroit.
So far, Polamalu has missed three games, or the minimum amount expected after Titans tight end Alge Crumpler fell on his knee during a blocked field goal attempt.
"Troy's been doing well and progressing well," coach Mike Tomlin said Tuesday. "Last week, he ran some in a straight line to pretty solid reviews. We'll take another step to see where he is. ... We'll get him back out there on the practice field and see how he responds to that."
The Steelers (2-2) already know how they've responded without Polamalu, and that's not very well.
Their defense, No. 1 in the NFL a year ago, allowed the Bears and Bengals to mount lengthy scoring drives that resulted in last-minute victories during the first two games Polamalu missed. Polamalu's replacement, Tyrone Carter, was in coverage during both of Chicago's touchdown drives.
On Sunday, the Steelers led 28-0 against San Diego, then had to withstand a 21-point Chargers fourth quarter to win 38-28. Chargers tight end Antonio Gates took advantage of Polamalu's absence to catch touchdown passes of 3 and 30 yards.
Asked whether Polamalu's absence made a difference during San Diego's comeback, Tomlin said, "I'm not going to dispute that, but at the same time I'm not going to use that as an excuse."
Still, the evidence is everywhere that the Steelers badly miss Polamalu, his versatility and his ability to take away the middle of the field from opposing offenses.
While winning the Super Bowl last season, the Steelers outscored opponents 104-75 in the fourth quarter; this season, they've been outscored 48-13. They've allowed only 30 points in the other three quarters.
They also have eight sacks through four games, compared to 15 a year ago.
A season ago, the Steelers had the NFL's best pass defense; now they're in the middle of the pack at No. 15, allowing 218.2 yards per game. The average was 156.9 last season.
As much as they miss Polamalu, the Steelers know they can't rush him back and risk a more serious injury that could put him out for the season. While they won't say so, they certainly expect to be able to beat Detroit (1-3) on the road and Cleveland (0-4) at home the next two weeks -- whether Polamalu plays or not.
What they don't expect is to be able to play like they did Sunday against San Diego and still win.
"Guys have got to do what they're supposed to do," nose tackle Casey Hampton said. "The plays are being called and guys just aren't getting it done. You can't point your finger at anyone, we're just not getting it done. That's uncharacteristic of us."
Maybe it's because they're out of character without Polamalu involved in their blitzing schemes. The Steelers aren't blitzing nearly as often or as effectively, and that might be where his absence affects them most.
"We've got to do a better job of making him [the quarterback] hold it a little longer," Tomlin said.
Running back Willie Parker (left toe injury) may be held out of practice Wednesday, as might safety Ryan Clark (strained lower back), linebacker Andre Frazier (sprained right shoulder), and left guard Chris Kemoeatu (sore left ankle). Tight end David Johnson (high ankle sprain) should return.
Tomlin hasn't decided how the carries will be divided between Rashard Mendenhall and Parker once Parker returns. Mendenhall ran for 165 yards and two touchdowns against San Diego.