Williams (concussion) was a limited participant in Thursday's practice, Nick Harris of the Fort Worth Star-Telegram reports.
Williams cleared the third step of the NFL's five-step concussion protocol Thursday by being cleared for non-contact practice. If the defensive tackle hopes to play Sunday, he will have to practice Friday and be cleared by an independent neurologist. If Williams can not be cleared of his concussion in time for Sunday's game, Kenny Clark and Solomon Thomas would be in line for expanded roles on the Cowboys' defensive line.