Correia was injured while making his fifth start of the season against Cincinnati on Saturday. He faced only three batters and threw nine pitches before feeling pain in his left side. Trainer Dave Groeschner, pitching coach Dave Righetti and manager Bruce Bochy rushed to the mound and checked on the pitcher, who was removed from the game.
An MRI exam later revealed Correia (1-3, 4.50 ERA) suffered an oblique strain that could keep him sidelined up to a month.
"He's got a pretty good strain in there so it's going to be awhile,'' Bochy said. "They just seem like they take forever to get rid of. You have to get rid of it completely before you can resume playing. That's a blow because our starters have been doing so well and Kevin's been throwing the ball well.''
Left-hander Pat Misch was recalled from Triple-A Fresno to take Correia's roster spot. Misch, who was scheduled to start for Fresno on Sunday, will initially work out of the Giants bullpen and could also be used as the team's fifth starter.
