The Giants placed right-hander Matt Cain on the 15-day disabled list on Friday. The hurler sustained a right forearm contusion on Thursday, when he exited his start in the fourth inning after being struck by a line drive.
To take Cain's spot on the roster, the Giants promoted right-hander Yusmeiro Petit from Triple-A Fresno.
Cain departed Thursday's contest after 3 1/3 innings. He allowed three runs on seven hits in San Francisco's 10-5 loss to Pittsburgh. Gaby Sanchez lined a pitch off the middle of Cain's arm.
"We are fortunate, and he is fortunate," said Giants manager Bruce Bochy, noting the injury could have been much worse. "That ball was smoked. But he's tough."
Cain has compiled an 8-8 record and 4.43 ERA this season. He has made every assigned start since joining the big league club in 2005.
Petit has appeared in one game for the Giants this season. In a relief outing in late July, he allowed two runs on six hits over 5 1/3 innings.