Matt Cain left after the third inning of Wednesday's game against the Rockies due to a possible right hamstring injury. Cain caught Charlie Blackmon looking to end the third, but he appeared to be in some discomfort walking off the mound after the inning. Yusemiero Petit started the fourth inning in Cain's place. The right-hander didn't allow a hit or a walk in his three innings of work, striking out three, before exiting. The Giants should update his status after the game.