PITTSBURGH — One sight you won’t see on the Pittsburgh Steelers’ sideline: The players mimicking those high school and college teams that hold up four fingers as a game winds down, signifying the fourth quarter belongs to them.

The Steelers (2-2) have faltered repeatedly in the fourth quarter this season, and it’s probably their biggest concern one-quarter of the way through a season in which their defense has yet to play up to its reputation.

Last season, the Steelers allowed only 75 points in the fourth quarter – less than a touchdown per game. That shutdown ability when games often are decided permitted them to rally and win late in the fourth quarter six times, and again in the Super Bowl against Arizona.

This season, the Pittsburgh defense can’t seem to get off the field when it counts. The Steelers have allowed 48 points in the fourth, 21 to the Chargers on Sunday night. The Bears and Bengals beat them with drives late in the fourth, and the Chargers gave them a scare before losing 38-28 in a game the Steelers led 28-0.

This isn’t the defense that Pittsburgh is accustomed to playing with Dick LeBeau as its coordinator –and it’s not entirely because the Steelers are lacking All-Pro safety Troy Polamalu.

He has missed the last three games and could miss a fourth Sunday in Detroit because of a torn medial collateral ligament in his right knee.

Polamalu did not practice with the Steelers regulars Wednesday or Thursday, a strong sign he won’t play in Detroit.

While not having Polamalu is a major disadvantage to what was the NFL’s best defense the last two seasons, it doesn’t explain all those faulty fourth quarters.

“It’s one thing here, one thing there,” defensive end Aaron Smith said. “It’s just a lack of focusing on the small details, I think. Part of it is making plays. This is the NFL and there are teams that are making plays.”

The Steelers defense has not been one of those units, at least during the fourth quarter. They have yet to give up a point in the first quarter, when they’ve outscored teams 31-0, and they’ve allowed only 30 points combined in the second and third quarters.

Once the fourth quarter arrives, offenses begin to solve them.

“It’s still a work in progress,” safety Ryan Clark said. “But Chicago, Cincinnati, you tell me what big play they made on those drives? What amazing things did they do? There’s nothing that anyone’s doing to us. We just need to make some stops.”

The pass rush also hasn’t been what it was a season ago.

LaMarr Woodley, who had 111/2 sacks during the season and six more in the playoffs, doesn’t have a sack. Turnovers are down, too; the Steelers have forced only three, compared to nine through four games a season ago.

According to Woodley, LeBeau is trying to find new wrinkles or a previously unused blitz that might make a difference.

“Every week is something different with coach LeBeau,” Woodley said.

With the Lions (1-3) and Browns (0-4) up the next two weeks, the Steelers might realistically expect that the fourth quarter won’t make a difference.

“A lot of people are looking at this week like it’s an absolute win, but it’s not like that for us,” Clark said. “We have to stay focused.”

Having former Steelers linebacker Larry Foote playing for the Lions may ensure that. Foote was one of the most popular players in the Steelers locker room before he signed with Detroit, his hometown team, and he’s planning to pull out some of his best trash-talking routines. He also promises to spare no one.

“They look like a totally different team, they look like a better team, a team that’s going out there fighting every weekend,” linebacker James Farrior said.

“Their record may not show it but they are an improved group. ... I think he (Foote) is sort of their leader out there on defense, and you can tell their defense is different.”

Having Foote in Detroit has gotten the Steelers’ attention, which might be exactly what they need going into a game they are expected to win easily as the NFL’s best team of a season ago meets what was its worst.

“For us, it’s about getting that first road win,” wide receiver Hines Ward said. “If you want to be a dominant team, you have to win on the road.”