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Green Bay --- Starting center JC Tretter will be out "multiple weeks" to a knee injury, but the injury is not believed to be long term.

The agent for Tretter, Alan Herman, indicated Sunday that this is "nothing surgical" and there is no ligament damage.

"I don't know what they're calling it yet," Herman said, "but it seems to be some type of bone bruise. ... I don't think it's anything that'll be an extended period of time."

Tretter sustained the injury early in Green Bay's 31-21 exhibition win over the Oakland Raiders on Friday night. Team physician Dr. Patrick McKenzie checked out Tretter's left knee between series in the first quarter, but he continued to play on.

The second-year pro out of Cornell completed his entire playing time -- 45 snaps -- before the pain truly began to set in.

"Once the ones went out of the game, and once he settled down, that’s when it started bothering him," McCarthy said. "It was bothering him at halftime, then when I got back in here after the game they ended up putting him on crutches.

"When I see J.C. Tretter on crutches, I think of him walking in here to work every single day since February and seeing what he’s put into it. B.J. Raji, he was in the best shape and having the best camp of his career. Don Barlcay, standing right next to J.C. every single day since February. So that’s the hard part about it, what the individual has to go through. This is not an issue for the whole team. This is the way the NFL is. Injuries are part of the game, it’s unfortunate."

Rookie Corey Linsley will take over as the starting center with Tretter out.

While Tretter has shown an ability to steer the Packers' no-huddle attack and get to the second level in the run game, Linsley has impressed coaches with toughness and personality.

"He’s going to do a heck of a job," McCarthy said of Linsley. "He’s obviously a rookie. I like his makeup. It’s just, he needs the reps. He’s just a pro each and every day, and he’ll be ready once we step on the field for Kansas City."

With Tretter, Herman has not heard exactly how long the recovery will take, saying it "could be three, four, five, six (weeks)." It depends how the Packers doctors treat the injury. But he repeated, it's "nothing significant."