This just in via twitter from Frank Hanrahan at ESPN 980:
Mike Williams will see his first NFL action since the 2005 seasons when he takes the starting lineup at right guard. This means that Chad Rinehart’s two-game stint at the position is over, at least for the time being.
The guess here is that they want to get Williams some game action and that the eventual move will be to put Williams at right tackle and Rinehart back in at guard.
I hope Tandler's guess is right, otherwise this means the team has given up on Rinehart