LAKE FOREST, Ill. – Charles Tillman won’t be on the field Friday when the Bears kick off training camp with a 3 p.m. practice at Olivet Nazarene University in Bourbonnais.

The veteran cornerback will be sidelined indefinitely after undergoing a procedure to remove a piece of disc fragment from his lower back two weeks ago. The Bears hope that Tillman, who also had shoulder surgery in January, will recover in time to start the regular-season opener Sept. 13 in Green Bay.

Charles Tillman leads all active Bears and is tied for 14th in team history with 20 career interceptions.

“I’ll be fine for the season,” Tillman said Tuesday at Halas Hall. “There’s no need to panic. When I panic, then you can panic. But I’m not panicking, so we’re good.

“[Things] happen. I’m just glad it happened now versus in the season. But I’m all right. I’m always optimistic."

Tillman, 28, will be placed on the physically unable to perform list Friday. It’s not the same as being put on the “PUP” list following final cuts, which requires players to miss the first six weeks of the season.

The Bears will be allowed to remove Tillman from the PUP list at any point prior to the deadline that requires NFL teams to reach the mandatory 53-man roster limit.

Tillman played well last season after missing significant portions of training camp while his infant daughter recovered from a life-saving heart transplant. 

The 2003 second-round pick started 15 of 16 games, registering 91 tackles and three interceptions while leading the Bears defense with four forced fumbles and 16 pass breakups.

With Tillman out, it's even more important for Nate Vasher to pick up in training camp where he left off in OTA workouts. Determined to revert to his Pro Bowl form after missing 20 of 32 games with injuries the past two seasons, the veteran cornerback had an excellent offseason.

In addition, Corey Graham is expected to spend more time at cornerback in training camp and the preseason after lining up at cornerback, free safety and nickel back during the offseason. Young cornerbacks Zackary Bowman, Trumaine McBride and rookie fourth-round pick D.J. Moore also figure to receive more opportunities to impress.