Packers linebacker Clay Matthews has had surgery after aggravating a right thumb injury in last week's loss to the Pittsburgh Steelers.

Coach Mike McCarthy said Friday that he didn't know when Matthews would return. The pass-rushing specialist has already been ruled out for Sunday's game against the Bears in Chicago for the NFC North title.

Matthews missed four games earlier in the season with the thumb injury. He was wincing in pain on the sideline after hurting the thumb again on a sack in the second quarter of the 38-31 loss to the Steelers.

Matthews finished the regular season leading the team with 7.5 sacks.