ST. LOUIS -- Three games into his Cardinals career, Mark DeRosa is hurt. He and the club are just hoping it's not too serious.

DeRosa injured his left wrist on a swing in the fourth inning of St. Louis' 6-3 loss to San Francisco on Tuesday night. He remained in the game for one more inning, but removed himself before taking another at-bat. He is expected to be reexamined on Wednesday.

"I took a swing there my second at-bat and felt a little tweak in my left wrist," DeRosa said. "I went in to hit off the tee after coming in from playing the field, and it just didn't feel right. I felt like I should come out of the game and get it looked at."

Pitcher Chris Carpenter was removed for a pinch-hitter in the bottom of the fifth. When the sixth inning started, reliever Josh Kinney slotted into DeRosa's spot in the batting order as part of a double-switch. Neither DeRosa nor manager Tony La Russa had any diagnosis beyond discomfort in the joint. DeRosa said he had never had an injury in that area before, so he did not know exactly what to make of it.

"I have no idea," he said. "There are so many small bones and stuff in the wrist. I don't know. But I didn't want to go out there and push it and find myself not being able to play for a little bit."

After taking Randy Johnson's first pitch of the at-bat for a ball, DeRosa swung and missed at a changeup from Johnson, at which point he felt pain. He finished the at-bat, fouling off two pitches and hitting one of them extremely hard into the seats down the third-base line.

"I was able to gut through it," he said. "It didn't hinder my swing at all. But it was something that was progressively getting a little more uncomfortable as I stayed in the game."