Mathis was injured late in last weekend's 30-27 victory over the Green Bay Packers. He tried to use a knee brace, and when that didn't work, he did not return. The team said then he had a sprained knee.
Mathis played defensive end each of his first nine NFL seasons and leads the Colts with five sacks this season. He is ranked eighth in the NFL in sacks in his first season at linebacker.