By Chris Emma–

LAKE FOREST, Ill. (CBS) — The Bears will be without a key piece of their defense for perhaps the entire season, with coach John Fox announcing Wednesday that linebacker Jerrell Freeman will require surgery to repair a torn pectoral muscle.

Fox couldn’t say whether Freeman may be able to return later this season. It’s unknown when he suffered the injury during the loss to the Falcons in the season opener Sunday. Approached by reporters Wednesday, the Bears declined to make Freeman available.

The Bears placed Freeman on injured reserve Tuesday and signed linebacker Jonathan Anderson off the practice squad. Nick Kwiatkoski is expected to fill Freeman’s role alongside Danny Trevathan at inside linebacker.

Fourth-round pick a year ago, Kwiatkoski played in 14 games in 2016 and made his debut during the third game of the season. He started in seven contests as Trevathan dealt with injuries and Freeman worked through a four-game suspension for performance-enhancing drugs.

“I feel a lot better about Nick right now than I probably I did in that (rookie debut) game last season,” Fox said of Kwiatkoski.

Freeman, 31, was voted a captain by the Bears entering this season. He had become a key figure to this defense, earning the trust and respect of younger teammates. Freeman had posted at least 110 tackles in his first four of his first five NFL seasons before this.

After losing Freeman, the Bears now have eight players on injured reserve and can designate two for a return as part of a new league rule.

Chris Emma covers the Bears, Chicago’s sports scene and more for Follow him on Twitter @CEmma670 and like his Facebook page.