LAKE FOREST, Ill. (AP) - The Chicago Bears defense has five starters 31 or older, and 34-year-old linebacker Brian Urlacher is coming off knee surgery a month ago.

Even so, they believe they have lost very little due to age and want anyone who doubts it to test them.

Urlacher was held out of Thursday's practice, but the plan is to practice Friday and play Sunday in the opener against the Indianapolis Colts.

Although Urlacher realizes his left knee will never be the same, he anticipates no diminished returns. The same goes for the "seasoned" Bears defense that's preparing for Sunday's game at Soldier Field against No. 1 draft pick Andrew Luck and the Colts.

Meanwhile, Collie says he's day to day for Bears game.

Indianapolis wide receiver Austin Collie wants to get going. But he is being cautious after his third diagnosed concussion since the start of the 2010 season. It came in the second preseason game, and he did not return to practice until Monday as the Colts get ready for Sunday's opener against Chicago.

Colts coach Chuck Pagano said Collie is "full go." Collie, however, would not say Thursday if he's been fully cleared, saying "there is no definite timetable."

Steelers linebacker Larry Foote buckled Collie with a hit during the Colts 26-24 preseason loss Aug. 19.