After getting at least three separate opinions, Casilla decided to have the surgery and clear things up. He said the discomfort altered everything about his pitching routine.
Giants manager Bruce Bochy said left-hander Jeremy Affeldt will assume most of the eighth-inning responsibility, while right-handers Chad Gaudin and Jean Machi will be in the mix for the seventh and eighth innings.
Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.