D.J. Moore injures his ankle

LAKE FOREST, Ill. -- Chicago Bears starting nickelback D.J. Moore missed practice on Thursday with an ankle injury, which raises serious concerns about his availability to play against the San Diego Chargers this weekend at Soldier Field.

The defensive back hurt the ankle near the end of Wednesday's practice session, according to Bears coach Lovie Smith.

"Yesterday at the end of the practice, towards the end of practice, D.J. Moore hurt his ankle and wasn't able to do anything today," Smith said. "We'll keep monitoring his progress."

Moore didn't contribute much his rookie season, but has become an important member of the Bears' defense over the last year and a half. He is currently tied for the team lead in interceptions (3) and is fifth in total tackles (44), despite rotating in and out of the game with strong-side linebacker Nick Roach.

The Bears are expected to frequently be in the nickel package on Sunday, considering the Chargers rank No. 4 in the NFL in passing offense (288.7).

In the event Moore is inactive versus San Diego, Corey Graham will fill the void at the nickel position. Graham replaced Moore, who was ejected, in the fourth quarter of the Bears victory over Detroit and made an immediate impact when he intercepted Lions quarterback Matthew Stafford in the end zone.

"It went pretty smooth [in the Lions game] because the last couple seasons I've still been practicing at nickel," Graham said. "I go to the meetings every week, so it's not like I don't know what's going on. I get coached up every week on it, so it went smooth. I already knew what to do, so I just went out there and did my job."

A Pro Bowl caliber performer on special teams, Graham started nine games at cornerback in 2008, and one contest the following season. Graham competed for the nickelback job in the summer of 2010, but lost out to Moore.

"It would be very exciting [to start on Sunday]," Graham said. "I've been looking forward to it for a long time. I hope I get an opportunity to go out there and play. I really want to go out there and play on defense. That's something I've wanted for a long time. I'm very excited about it and just hope I get the opportunity."

Starting cornerback Tim Jennings can also move inside and play the nickelback spot, according to Smith, but that would require the Bears to change two positions on defense, instead of simply swapping out Moore for Graham.

Meantime, defensive end Julius Peppers returned to practice on Thursday after resting his sore knee the previous day.

Jeff Dickerson covers the Bears for ESPNChicago.com and ESPN 1000.