Berkman first felt something amiss during Sunday's loss to the Pirates, and he sat out Monday's home game. He returned to the lineup on Tuesday but took only two at-bats before feeling a recurrence of the discomfort when he grounded out in the fourth inning. The issue is in the area of the rotator cuff of his non throwing shoulder.
"Honestly, I thought I was going to be fine today," Berkman said. "When I got out there in the game, I took that swing. It's concerning to me, just because I don't want to do something and really hurt myself. It's like a pinch. When you go to accelerate, it's just there. It's like any kind of a strain. It doesn't feel good."
Skip Schumaker moved from second base to the outfield to take Berkman's place, with Nick Punto coming in to play second base. The Cardinals were already doing without Matt Holliday, who has an illness that kept him out of Tuesday's game.
"He felt like he couldn't take a real good swing after that second at-bat," manager Tony La Russa said. "He said he'd hang around, and I said, 'Why? If you're not going to swing, we may as well put the defense in right now.'"
Berkman will receive an MRI exam on Wednesday, with the idea being to determine the exact location of the issue. That would then allow the doctor to give him an injection to ease the discomfort. A shot would likely sideline Berkman for two or three days.
"If they can pinpoint the muscle that is giving me trouble, they can inject it and it helps speed the recovery process," Berkman said. "Nobody thinks it's anything to be that concerned about.
"I think they're just going to look at it first and then they'll tell me what's the best thing to do."
Matthew Leach is a reporter for MLB.com. Read his blog, Obviously, You're Not a Golfer and follow him on Twitter at @MatthewHLeach. This story was not subject to the approval of Major League Baseball or its clubs.