Troy Polamalu wasn't necessarily choosing sides or supporting running back Willie Parker's contention that the offense relies more on the pass and has drifted away from Steelers football.

But the four-time Pro Bowl safety reiterated a point he made at the beginning of last season -- the Steelers' top-ranked defense isn't built to be on the field for an extended period because it relies on speed, aggressiveness and disguise to be successful.

Polamalu said the defense requires a certain style of offense to be effective -- one that possesses the ball.

"If you take the best offense, I don't know, say, New Orleans, and you take us as a defense, that's not necessarily going to make the best team," Polamalu said. "The reason why is, they may pass the ball a lot, but, if they go three-and-out, three-and-out, three-and-out and score a touchdown fast, that's not the way our defense plays, that's not the way we play.

"We swarm to the ball, we play man-to-man a lot, we always have our back turned [to the ball], we're always playing high-intensity football. You take a team like Indianapolis, for example, which is always dropping back, always has vision [at the quarterback], always zone-dropping, you don't need nearly as much energy [to play that defense].

"You could probably count how much they actually run and compare how much we have to run, and it may be two games to one, in that sense. Not only that, we play a very physical brand of football. We're not meant to be out there very long."

During their four-game wining streak, the Steelers' offense has averaged 33 minutes, 5 seconds in time of possession, nearly two minutes higher than their season average (31:23).

Even so, their season average is higher than when the Steelers won the Super Bowl in 2005 (31:16) but lower than when they were 15-1 in 2004 (34:00).

"The personality of us, whenever we've had success around here, is running the football," Polamalu said. "When we were 15-1, our quarterback was maybe throwing 15 times a game, and there were like five screens and two or three checkdowns. We didn't have nearly as good a defense then, even though we were No. 1, as we do now.

"Steelers football is about playing good defense. That's how it all works together."

Keisel unlikely to play, but Davis due to play

Defensive end Brett Keisel (knee) has not practiced all week and is expected to miss his third consecutive game. He will be replaced by defensive end Travis Kirschke. Fullback Carey Davis (calf) was not limited in practice and is expected to play against the Ravens.

Ravens quarterback Joe Flacco didn't look like much of a rookie in his first meeting with the Steelers, especially considering it was his first NFL game on the road.

Flacco completed 16 of 31 passes for 192 yards and one touchdown -- a 4-yard pass to tight end Daniel Wilcox. He completed 3 of 3 passes for 50 yards on the touchdown drive in the fourth quarter that forced overtime.

His passer rating of 81.7 was the fourth best against the Steelers' No. 1 defense this season. What's more, he was not intercepted.

"The main thing he showed me from that game is he couldn't easily be rattled," said inside linebacker James Farrior. "We had a lot of buzz going in how we were going to try to confuse him and rattle him a little, but he stuck with it, he stayed in there. We showed him a lot of different looks and we didn't confuse him too well."

The Steelers have managed to force many of the league's top quarterbacks into their lowest passer ratings of the season, including Philip Rivers (43.6), Matt Cassel (39.4) and Tony Romo (44.9). Not Flacco.

"It surprised me," Farrior said. "Anytime you get a rookie quarterback going against our defense for the first time, we expect a lot of good things to happen. I can't even remember a quarterback playing even close to that type of level he played at."