Matt Cain, Santiago Casilla hurt

DENVER -- San Francisco Giants starter Matt Cain and reliever Santiago Casilla both strained their right hamstrings in Wednesday night's 5-1 win over the Colorado Rockies and will undergo MRIs to determine the severity.

"The win was great," Hunter Pence said, "but it's a huge blow to lose Cain and Casilla."

The MRIs are set for Thursday, but Casilla told teammates he expects to be placed on the disabled list, the San Jose Mercury News reported.

Cain had good command and was cruising along, not allowing a hit through three innings. Then, on his last pitch of the third, he felt a twinge in his hamstring. The right-hander was replaced by Yusmeiro Petit to start the fourth.

Casilla was hurt in the ninth inning when he tried to beat out an infield hit, falling over the bag and rolling several times on the field. He was helped to the dugout by the trainers and was replaced on the mound by Jeremy Affeldt, who finished the game.

Just moments before in the dugout, Giants manager Bruce Bochy had told Casilla to not even bother swinging -- just take it easy at the plate.

"I was shocked he was running like that," Bochy said. "Guess he thought he had a hit. I don't know what got into him. Never seen him run like that."

Rockies second baseman DJ LeMahieu sent a sharp comebacker toward Cain in the third, but the ball appeared to glance off the pitcher's glove. Cain quickly scooped up the ball and threw out LeMahieu at first. The Giants checked on Cain, but he remained in the game to finish the inning. Cain said after the game that had nothing to do with his hamstring injury.

Cain also struck out three and hit Justin Morneau with a sailing fastball before exiting.

Cain missed 13 games earlier this season after he cut his right index finger as he made a ham-and-cheese sandwich in the Giants' clubhouse. The cut didn't require stitches.

Optimistic this injury will heal fast?

"We'll see how tomorrow it feels," Cain said. "Still got some adrenaline going. But it's calming down."

Bochy also said Buster Posey (nerve irritation in lower back) is "doing a lot better" and the catcher could be in the lineup Thursday. In addition, infielder Marco Scutaro (strained lower back) had a platelet-rich plasma injection and will take a week off before resuming his rehab.

The Associated Press contributed to this report.