The Green Bay Packers will start the 2014 regular season without starting center JC Tretter, who sustained what coach Mike McCarthy termed "a significant knee injury" in Friday's 31-21 preseason win over the Oakland Raiders.

Tretter, 23, didn't play at all during his rookie season because of a broken ankle suffered on the first day of organized team activities. Since Evan Dietrich-Smith departure to Tampa Bay in free agency, he's worked as the starting center throughout the offseason program and in camp.

ESPN Wisconsin reported Tretter didn't suffer any ligament damage and shouldn't be sidelined more than six weeks. There was initially some concern the injury may have been more severe.

Rookie Corey Linsley, a fifth-round pick in May's draft, took his first-team offensive line Sunday next to veteran guards Josh Sitton and T.J. Lang.

The news of Tretter's injury comes after the Packers discovered defensive lineman B.J. Raji will miss the entire season with torn right biceps and swing tackle Don Barclay's reconstructive knee surgery.

"It's a bummer, man. We felt like we were doing a lot of good things as an offensive line." Lang said. "It hurt when Donny went out and this one hurts, too. Like we're always saying, there's nothing you can really do about it. You've got to move on. Corey's been taking a lot of reps today and he's a guy who's come a long way since OTAs started. Hopefully we get J.C. back, but until he comes back, we're going to have to find a way to fill the spot."

Tretter had his left knee examined by team doctor Patrick McKenzie after the first drive Friday, but returned to play 45 snaps with the first-team offense. Linsley said he didn't receive word of Tretter's impending absence until Sunday.

"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."

-- whodkiew@pressgazettemedia.com and follow him on Twitter @WesHod.

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