NFL rosters change frequently from season to season due to salary cap restrictions, free agency and the draft, yet the Pittsburgh Steelers are an anomaly during a time when one bad game or one bad season can cause a team to shed a player.

When they began practicing Wednesday for their game at Tennessee on Sunday, all 11 players who started on defense for them during the Cardinals-Steelers' Super Bowl two seasons ago were on the field. Ten of the 11 remain starters; only linebacker Larry Foote is a backup.

By contrast, the Cardinals have only four holdover starters, although linebacker Clark Haggans would be among that group if he hadn't missed the Super Bowl with a foot injury.

That 2008 Steelers defense was one of the best in NFL history, leading the league in overall and passing defense while giving up the fewest points — despite playing one of the most difficult schedules of any Super Bowl winner, opposing the Ravens (twice), Chargers (twice), Cowboys, Patriots, Eagles, Giants, Titans and Colts.

This defense matched that '08 level of performance by holding Atlanta without a touchdown during a 15-9 overtime victory Sunday in which the Falcons ended only one drive inside the Pittsburgh 20-yeard line.

"I don't compare our seasons like that, but it was a good start for us," linebacker James Farrior said Wednesday. "I think everybody was on their stuff during that game. We've just got to keep it up. It was similar, but we've got a long way to go."

Of course, this defense is accustomed to being together for long stretches.

By deftly managing the salary cap, the Steelers have kept defensive end Aaron Smith for 12 seasons, nose tackle Casey Hampton for 10; Farrior, defensive end Brett Keisel and backup lineman Chris Hoke for nine each, safety Troy Polamalu and cornerback Ike Taylor for eight apiece, linebacker James Harrison for seven, and linebacker LaMarr Woodley and safety Ryan Clark for five seasons. Inside linebacker Lawrence Timmons is the least-experienced starter, and he's been with them for four seasons.

Seven of the 11 starters are 30 or older, and Polamalu and cornerback Bryant McFadden both turn 30 next year.

Many teams are reluctant to accumulate so many players above the age when performance can begin to decline and injuries become more frequent. However, the Steelers are reluctant to break up a unit that statistically was No. 1 in 2007, 2008 and 2004 and has finished below No. 5 only once since 2003.

Defensive coordinator Dick LeBeau is 73 and, understandably, is sensitive to questions about how age affects performance. He suggests his defense draws motivation from the frequent talk it's getting too old to remain among the best.

"We're going to let the season speak for us on that," he said.

With Polamalu and Smith out with injuries much of last season, the Steelers played below their usual level by losing five times after leading in the fourth quarter. The Falcons game suggests the Steelers are significantly improved with Polamalu and Smith back, but a single game against an opponent that doesn't see them very often can be misleading.

Opposing the Titans (1-0) could prove to be a better indicator of where this defense is. The Titans were the only team to beat the Steelers decisively in 2008, winning 31-14.

"Honestly, I can't even remember that game. We played them last year in Heinz Field and won in overtime (13-10), and that was a whole different makeup," wide receiver Hines Ward said. "This team is different."

Pittsburgh also will be without quarterback Ben Roethlisberger as he serves the second game of his four-game suspension for violating the NFL's personal conduct policy.

Titans quarterback Vince Young hasn't opposed the Steelers before as a starter, but he understands what he's getting into from watching on tape — a defense that knows what it's doing and does it as well as any unit in the league. He saw that by watching the Falcons offense struggle to give quarterback Matt Ryan enough time to dodge Pittsburgh's frequent blitzing and throw enough accurate passes to mount a consistent offense.

"You have to be very patient and take what they give you, until something breaks," Young said. "I have a lot of respect for them. This is my first time and I'm definitely looking forward to it because you always want to test yourself against the best. That is how much respect I have for those guys."