Chicago Bears defensive tackle Dusty Dvoracek is going on injured reserve with a torn ACL in his right knee.

On Friday, Dvoracek underwent arthroscopic surgery after initial tests were inconclusive about damage to his right knee from Saturday's preseason game with the New York Giants.

Dvoracek, a fourth-round draft pick in 2006, went on IR as a rookie with a preseason foot injury, tore his left anterior cruciate ligament in the 2007 season opener with San Diego and last year played 12 games before going out for the season with a torn biceps.

"Right off the top of my head, I haven't seen a lot of players go through that," Bears coach Lovie Smith said. "Guys deal with injuries always. As much as anything, with Dusty, though, it's one thing to have injuries and they continue to linger. These are different things.

"He's getting things fixed. So really, once he comes back from this he should be as good as ever, so he should still have all of his options open."

Dvoracek, who is in the final season of a four-year contract, should be all right to continue workouts in seven to 10 months. Last season, Dvoracek led the Bears defensive line with 40 tackles at the time of his injury.

This preseason, the 6-foot-3, 303-pounder had been battling second-year player Marcus Harrison for the starting nose tackle position. The two are backed up by third-year player Matt Toeaina, whose chances of making the roster have now improved.

"I hate to see this happen to Dusty again, but I've definitely got to take advantage of the opportunity," Toeaina said.

Toeaina has played in four NFL games and was signed by the Bears off Cincinnati's practice squad late in the 2007 season.

"My opportunities have been limited, but like they say, you can't count your (practice) reps; you've got to make your reps count," Toeaina said.

He credited new defensive line coach Rod Marinelli with drastically improving his play this season.

"With coach Marinelli we've actually learned a lot more when he got here," he said. "So I feel like what I knew before wasn't much, and now thanks to coach Marinelli, I have a lot of knowledge of the opposition."

NOTES: Defensive end Israel Idonije missed Friday's practice with a sore hamstring and his status for Sunday's game in Denver is uncertain. Defensive end Alex Brown, who missed Thursday's practice with a sore hamstring, returned for Friday's workout. The Bears have a quick turnaround after Sunday's game, with a Thursday preseason finale at Soldier Field against Cleveland. As a result, they'll have only one practice next week prior to playing.