Williams left the game after tearing his left pectoral muscle in the third quarter of the Bears' 27-21 victory.
Rookie Jon Bostic went in for Williams and will take over at middle linebacker.
Bostic, a second-round choice out of Florida, started the first three games of the season for Chicago while Williams recovered from a calf injury sustained during the pre-season.
Williams signed with the Bears in March after eight seasons with the Denver Broncos.
He had 27 tackles, two sacks and one forced fumble in six games this season.
Chicago is 4-2, in first place in the NFC North. The Bears next play the Washington Redskins on the road Oct. 20.
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