INDIANAPOLIS -- Dominic Rhodes, the Indianapolis Colts' leading rusher last year, will miss this season because of a torn anterior cruciate ligament in his right knee.

Rhodes was injured while running a sideline pass route during the final 30 minutes of practice Thursday night.

An MRI taken Friday night revealed the injury, and an announcement was made Saturday, shortly before the start of the Colts' first home exhibition game against Cincinnati.

Following the injury, Rhodes lay on his back as team doctors tested the knee. He then limped, without assistance, to the locker room and did not return. He also was not at practice Friday, when the Colts finished their three-week training camp at Terre Haute, Ind.

Last season, Rhodes set an NFL rushing record for undrafted rookies with 1,104 yards after he replaced two-time rushing champ Edgerrin James.

Rhodes broke into the Colts starting lineup seven games into last season after James tore the ACL in his left knee and missed the rest of the year.

The Colts had considered going from their normal one-back formation to some two-back formations, using James and Rhodes together. Rhodes also expected to see some time at wide receiver and return kickoffs.

The return job may now fall to Troy Walters, claimed off waivers from Minnesota in March. Walters averaged 23.3 yards on 48 returns in two seasons with the Vikings.

Although James practiced for three weeks during camp, he still has not carried the ball in a game. New coach Tony Dungy held James out of the Colts' second preseason game Saturday, a 22-10 loss to the Bengals.

Rhodes is the second Colts running back to be lost for the season this week. Sixth-round draft pick Brian Allen injured his left knee in practice, and after missing almost a week of practices, had surgery Thursday to repair the lateral collateral ligament. Allen was placed on injured reserve on Saturday.

The rash of injuries has left the Colts thin at running back, which was expected to be one of their deepest positions.

On Saturday, the Colts had just three healthy running backs available: Jim Finn, Ben Gay and Wes Ours. They ran just 13 times for 45 yards.

"It's disappointing for Dominic and we feel really bad for him,'' Dungy said. "Usually with good teams, these kinds of situations act as a springboard for someone to play well.''

Even so, Polian said the Colts will search for a replacement.

"We're going to do nothing precipitous,'' he said. "You don't do anything but keep on, keeping on.''

Rhodes also dislocated his left shoulder during training camp but did not miss a practice. He had a partial dislocation of his left shoulder, which he has said has been a chronic problem, last year during a game against Miami. He missed one quarter before returning.