Ian Kennedy left Thursday's start against the San Francisco Giants after straining his left hamstring while making a pitch in the third inning.
The San Diego Padres right-hander signaled to the dugout that something was wrong, and manager Bud Black and a trainer went out to the mound. Kennedy was pulled immediately.
Kennedy said he "felt something grab, almost like a cramp feeling" on his final pitch.
"The whole time I felt something wasn't right. The last pitch, I didn't feel anything pop or anything but I'm not going to hurt my arm by changing my mechanics," he said.
"I needed to stop because I wasn't putting out the same effort because I was trying to protect it. It's frustrating because I felt really good and pitching in a great atmosphere."
Via Associated Press