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 his work ethic, wide 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 recently said 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 started the season on the active roster and played in three games, catching six passes for 29 yards. He was cut last week and added to the practice squad after clearing waivers.
Copyright 2010 by The Associated Press