Matt Williams has been let go as well...And Bob Melvin gets fired.
Honestly this is a move that had to be made. Not that this Giants' team was the most talented, but they were one of the most fundamentally unsound groups of players I've ever seen in the orange and black. At least don't beat yourself. Kudos to Buster Posey for making the change.
[Edit] Bruce Bochy is out of contract in Texas and there are rumors Posey will want to bring him back to SF. I'd rather not.