LAKE FOREST, Ill. – Bears defensive coordinator Bob Babich turned his players loose Sunday night in Indianapolis, and the result was a dominant performance that fueled a rousing 29-13 win over the Colts.

“Our mentality is that we’re going to attack, whether it’s through technique or a call or tackling somebody,” Babich said. “We want to be very aggressive. Our guys are very confident. They’re a good defense. We have a lot of good players on defense and their confidence never wavered.”

The Bears defense smothered running back Joseph Addai and the Colts Sunday night in Indianapolis.

The Bears played virtually the entire game in their nickel defense with linebackers Brian Urlacher and Lance Briggs up at the line of scrimmage where they could blitz Colts quarterback Peyton Manning or drop into pass coverage.

“We were aggressive the whole game,” said Urlacher, who tied Briggs for the team lead with nine tackles. “We were up at the line of scrimmage the whole game and got some pretty good pressure. Our DBs did a good job covering them and we stopped the run.”

The defense limited the Colts run game to 53 yards on 15 carries and generated three game-changing plays. 

Charles Tillman stripped the ball from Marvin Harrison and Briggs returned the fumble 21 yards for a touchdown. Adewale Ogunleye dropped Joseph Addai for a two-yard loss in the end zone for a safety and teamed with Briggs to stuff Dominic Rhodes for a two-yard loss on fourth-and-one from the 50 early in the fourth quarter.

The Bears appeared to confuse Manning, who completed 30 of 49 passes for 257 yards with 1 touchdown, no interceptions and an 81.8 passer rating that was identical to the one he registered in Super Bowl XLI. But without a complementary ground game, Manning was able to lead the Colts to only one touchdown on 10 possessions.

“We wanted to get a lot of people at the line of scrimmage,” said safety Mike Brown, who registered five tackles and broke up one pass. “We gave them a lot of looks and ran a lot of different things out of those looks.

“We were in zone [coverage], we were in man, pretty much everything. We tried to make everything look the same and we tried to keep them guessing because when [Manning] knows what you’re in, he’ll cut you up. He puts them in the right plays. But we were able to make everything look the same and hopefully we confused them a little bit.” 

The Bears were able to employ their nickel defense because they viewed tight end Dallas Clark more as a third receiver than a sixth offensive lineman. Clark exited in the first quarter with a knee injury, but the Bears continued to play with five defensive backs, rotating Brandon McGowan and Danieal Manning at the nickel position.

“It was a great game plan we put in and we put in some good stuff to kind of get after them a little bit,” Brown said. “It worked out for us. We played with enthusiasm and energy and our front four played unbelievable. When they play well, we usually have a pretty good game.”

Executing their aggressive game plan, the Bears dominated an undermanned Colts offensive line that was missing three-time Pro Bowl center Jeff Saturday and rookie guard Mike Pollak.

“That’s kind of our mantra: attack,” said defensive tackle Dusty Dvoracek. “We wanted to establish a new line of scrimmage and that was one of the keys to winning. Stopping the run and then getting heat on Peyton, that’s what we focused on all week in practice and came out here and did it.”

The stifling performance came after the defense struggled in the preseason against inexperienced quarterbacks such as the 49ers’ J.T. O’Sullivan and the Browns’ Brady Quinn.

“I really can’t explain how or why we turned the switch on," Tillman said. "I’m just glad we did turn it on because it really counts now. I’m going to give all the praise to coach Babich and the defensive coaches. They did a great job of putting us in situations for us to make plays."