Thanks to Frank Cuatro Ocho for getting the initial FanShot on the injury up early early this morning. The 49ers just sent out a press release announcing that Thomas Clayton did in fact tear the ACL in his right knee. However, on top of that they have now waived Clayton and filled his roster spot with FB Bill Rentmeester, a rookie free agent. I'm sure some folks think we should fly a flag at half mast for Clayton after his previous preseason performances.
If this isn't a sign of how far down the depth chart Thomas Clayton was, then I don't know what is. Although I could be wrong on the roster rules, the team could have placed Clayton on Injured Reserve as they have done with other preseason injuries in the past (notably Jay Moore the last two seasons). To not do so shows that was it for him. Unfortunately for Clayton, this is just one of the breaks of the game.
In terms of roster implications, there really isn't much there. He was competing with Kory Sheets for a roster position that might not even exist. Sheets has done enough to move up the depth chart a little bit and will need to continue showing coaches he's worth holding onto as more than just a practice squad body.
UPDATE: Thanks to save10 for pointing this out in Maiocco's article about the roster move:
Any team can claim Clayton, but that seems unlikely because he's out for the season. If he goes unclaimed, Clayton automatically reverts back to the 49ers and will go on injured reserve. If the 49ers had just placed Clayton on injured reserve without the "waived" designation, he still would have counted against the team's 80-man limit until the first cutdown day (Sept. 5).