Thomas was one of three pass-catchers taken in the second round two years ago in what has turned out to be an extremely disappointing draft by then-front office head Vinny Cerrato.
Thomas had trouble running routes correctly and was dogged by questions about work ethic; receiver Malcolm Kelly hasn't been able to stay healthy and is on injured reserve; and tight end Fred Davis is stuck behind Chris Cooley.
This year, Thomas couldn't make inroads despite a wide open No. 2 receiver competition that still hasn't been adequately filled. Offensive coordinator Kyle Shanahan said recently that Thomas needed to take a more professional approach to practice to earn playing time on offense.
Thomas has no catches this season but he had 12 kickoff returns for a 28-yard average.
Williams was promoted because the Redskins were down to two healthy running backs -- Ryan Torain and Chad Simpson -- after Clinton Portis was injured in last week's game. Portis hurt his left groin and is out four to six weeks.