Grabow, who last pitched Friday in Cincinnati, giving up three runs on four hits over one inning, had an exam on Saturday. He threw on the side Monday and Lou Piniella said he'd like to give the lefty at least one more day if possible.
"It's something I've been pitching through for a while," Grabow said. "It's been bothering me for a few weeks now. I tried to pitch through it and thought it would go away, but it didn't go away."
Grabow said he's never had this kind of discomfort before and wanted to treat it as soon as possible.
"He's ready to go," Piniella said of the reliever, who has a 9.26 ERA.