Before the Indianapolis Colts played the Pittsburgh Steelers nine days ago, most of the talk centered on the physical nature of Pittsburgh's running game. Conventional wisdom indicated that the Colts' undersized, so-called finesse defense would be hard-pressed to stop the Steelers from controlling the ball and the clock, while keeping Peyton Manning and the offense off the field.

So much for conventional wisdom and finesse.

The Colts, in dominating the Steelers 26-7, stuffed the running game, often bringing eight players close to the line of scrimmage and holding Pittsburgh to 86 yards rushing. They also sacked Steelers quarterback Ben Roethlisberger three times, pressured him all night and intercepted two passes.

"I hope by now people will really see that we're going to play as tough as anyone," free safety Bob Sanders said after the Steelers game. "I don't really know what it's going to take for us to shake that label, but if you play us you find out we're not trying to finesse anything."

"Whatever labels people want to put on us, that's on them," defensive tackle Montae Reagor said. "We feel like we can play any style we have to play. What people ought to realize is we're always going to play hard and with intensity. There isn't anything finesse-ful about us."

In their 45-28 victory over St. Louis on Oct. 17, the Colts certainly made a searing impression on Rams wide receiver Torry Holt.

"They are the most active defense right now in the National Football League," said Holt. "Their safeties fly around, their corners fly around, their defensive ends twist and turn and spin and fly around. Their linebackers are fast as hell and they fly around. They get picks and knock people out. I think they are playing with a great deal of passion and speed, and that can be intimidating to teams across the league, because you say, 'We're going to run the ball? No. We're going to pass the ball? No, they're too fast, they pick things off. So what do we do?' They put teams in a staggering position and they don't ever change, they just play and they just fly around and most importantly, again, they play with a great deal of confidence and passion."

Trying to become the NFL's first undefeated team since the 1972 Miami Dolphins, a team with another undersized and mostly no-name defense, the Colts have built this unit to Coach Tony Dungy's specifications, generally sacrificing bulk for speed. The unit gets even faster playing at home on the RCA Dome's artificial turf, though Dungy insisted that he and General Manager Bill Polian have always believed in the importance of speed over size on defense.

A college quarterback at Minnesota in the early 1970s, Dungy has long been considered one of the game's best and brightest minds after switching to defense and playing safety for the Pittsburgh Steelers' 1978-79 Super Bowl champions. His defensive philosophy has always been linked to the old Steelers system, another unit that flew to the football and seriously pressured quarterbacks.

"You defend the run on the way to the passer," Dungy told the Dallas Morning News last month. "Chuck Noll always looked for striking ability. They didn't necessarily need to be big guys. . . . Jack Lambert was a 205-pound middle linebacker. But they would play low and hit with the top of their pads. Tough guys. That's what I've always looked for. Not necessarily the biggest guys in the world, but guys who are tough and can strike."

The Colts also have another defensive edge playing indoors and are likely to have home-field advantage throughout the AFC playoffs. With only 55,000 seats, the RCA Dome is the smallest stadium in the league, but fans have made it one of the loudest, especially when opponents have the ball.

"I believe the [Colts] fans now have an understanding of the type of impact they can have as it relates to the Colts being on defense," Tennessee Coach Jeff Fisher said last week. "It really doesn't matter who the [offensive] tackle is out there or how good he is. He's going to have a hard time if he can't hear."

Still, it took awhile to get to this point. In Dungy's first three years, the Colts gave up at least 300 points a season, even though they made the playoffs each time and were 35-13 in the regular season. Last year, they gave up significant yardage but relied more on big plays, forcing 36 turnovers and finishing with 45 sacks, both tied for third in the league.

But in training camp last summer, Dungy said he saw something new in the defense -- dependability in key moments.

"When I came here, we looked for speed," Dungy said. "If guys had explosion and they could run, it was always a plus. It plays into our stadium and to our surface. I'm very proud of these guys [on defense]. They've worked hard for four years to get there. There are not a lot of high-profile guys, but they fit in for us. They work well together, they have a lot of pride, and they get better and better."

Quarterback Peyton Manning has joked this season that he has been able to "sleep a lot better on Saturday nights" knowing that his defense can bail him out when the offense bogs down, which doesn't happen very often.

The Colts have made dramatic defensive strides since the 2004 season. Last year, the Colts finished 29th in total defense in the NFL, 24th against the rush and 28th against the pass. With four games left, they are third in total defense, ninth in rushing defense and ninth in pass defense.

In yardage allowed, the difference is even more dramatic. In 2004, teams averaged 127.3 rushing yards per game; this year that's down to 97.2 yards. Last year, the Colts yielded 243.2 passing yards per game; this season it's 185.3 yards. Overall, the Colts are allowing opponents 88 fewer yards per game. And they're still forcing plenty of turnovers, with 15 interceptions and seven fumble recoveries and a plus-eight figure on the give-away/take-away charts, fourth-best in the AFC.

Ted Marchibroda, a former Colts and Baltimore Ravens head coach who is the color analyst on the club's radio network, cites several reasons for the improved defense.

"First, they're maturing, getting older and most of them have at least three or four years experience in this system under their belt," he said, adding that the late-summer addition of Corey Simon, a former Pro Bowl defensive tackle with the Eagles, "has added veteran leadership and great experience to the ballclub. The free safety, Bob Sanders, has had a real impact just in the way he plays. He's very physical and he seems to set the tone for the rest of them. He's done it all year long. He and [strong safety] Mike Doss have added a real physical presence.

"They're well-disciplined and once they get a lead, it's tough for teams to catch up. They play a lot of cover two [with the two safeties taking each side of the field]. The safeties will play deep and the linebackers are athletic enough to take deep drops into pass coverage. If you can run on them enough so that a safety has to come up closer to the box, then maybe you have a chance."

But the Indianapolis defense has not allowed a 100-yard rusher in 14 straight games, though Bengals running backs Chris Perry and Rudi Johnson did combine for 158 rushing yards, the highest total the Colts have allowed all season.

The Colts also put tremendous pressure on opposing quarterbacks, especially with their defensive ends. Robert Mathis, ultra-light at 235 pounds and used mainly in passing situations, is tied for third in the NFL in sacks with 101/2, and Freeney, arguably the most explosive defensive end in the game, is tied for fifth with 91/2 sacks a year after he led the league with 16. Both are particularly effective at home, where the crowd makes it virtually impossible for offensive tackles to hear the snap count.

"They're just really athletic and fast up the field," Titans tackle Michael Roos said of Freeney and Mathis last week. "They like to spin and run a lot of twists. It makes it hard and forces you to have really good technique against them."

Said Steelers offensive tackle Trai Essex: "On that fast turf, with the crowd noise, they pose problems. When you look at Freeney, he runs like a wide receiver or a defensive back. That's how fast he is. He has a low center of gravity that also makes it difficult to push him out of his path."

Still, like the Steelers' defenders of the 1970s, the Colts are hardly physically imposing. In addition to Mathis, there's middle linebacker Gary Brackett (5-11, 235 pounds); weakside linebacker Cato June (6-0, 227 pounds) and cornerback Jason David (5-8, 172 pounds). At safety, Doss is 5-10 and 207 pounds and Sanders is only 5-8 and 206, but both know how to throw their weight around.

"He's a solid tackler and a physical football player," Ray Sherman, the Titans wide receivers coach, said of Sanders last week. Teamed with Doss, Sherman added: "Those are probably two of the best safeties in the league right now the way they're playing. They don't miss tackles. Both those guys are very smart. They always seem to be in the right position and they do a great job of timing up the quarterback's cadence so they can penetrate the line of scrimmage and make plays."

Dungy, who built a strong defense at Tampa Bay, knows how it can take pressure off the offense.

"When I first got here, we were not a team that was relaxed if it was a low-scoring game," he said. "If our offense didn't put points on the board early, we got a little antsy. We've been able to work our way through that. I think we've got more confidence playing different style games now than we did four years ago."

Staff writer Jason La Canfora contributed to this report.

Raheem Brock (79) and the Colts have the NFL's "most active defense right now," said the Rams' Torry Holt.Dwight Freeney and mates have had much to celebrate, ranking high in several key categories.Robert Mathis, shown hitting the 49ers' Alex Smith, is tied for third in the NFL with 101/2 sacks.