Casilla out at least a month with hamstring strain

DENVER -- The Giants announced Thursday that right-hander Santiago Casilla, their top setup reliever, is expected to miss at least four weeks with a strained right hamstring.

Casilla injured himself while running to first base during an inconsequential ninth-inning at-bat in San Francisco's 5-1 victory over Colorado on Wednesday. He underwent an MRI on Thursday that revealed a Grade 2 (medium) sprain.

The Giants placed Casilla on the disabled list and recalled right-hander George Kontos from Triple-A Fresno to fill the bullpen vacancy. Kontos appeared in 14 games for Fresno, compiling an 0-2 record with a 3.80 ERA. In 23 2/3 innings, Kontos accumulated 35 strikeouts while issuing only three walks.

Kontos had to leave himself a 3:45 a.m. PT wakeup call to catch his flight to Denver. But, he said, "You're never quite as tired when you come back to the big leagues."

Kontos, who began his second stint of the season with the Giants, was less than thrilled about the misfortune that prompted his return.

"It's a shame that you lose a guy to something as freakish as that," he said.

Losing Casilla threatens to rob the Giants of the bullpen depth that has hastened their success. He had a 1.37 ERA in 22 appearances.

Manager Bruce Bochy said that he will rely on a combination of relievers -- left-handers Jeremy Affeldt and Javier Lopez, as well as righties Jean Machi and Juan Gutierrez -- to handle Casilla's setup responsibilities in his absence.