In Week 5, Williams collected a season-high four combined tackles and a sack during a 14–13 victory at the Tennessee Titans. On October 18, 2015, Williams recorded one tackle before sustaining a knee injury and was carted off the field in the second quarter of a 34–21 loss to the Cincinnati Bengals in Week 6. His injury was initially suspected to be a sprained PCL. On November 27, 2015, it was reported that Williams would have to undergo surgery to repair his meniscus after his injury did not respond to initial treatments. On December 1, 2015, Williams was placed on injured reserve. Williams finished the 2015 season with 14 combined tackles (six solo) and a sack in six games and six starts.