Twins closer Glen Perkins said he felt 90 to 95 percent during his last outing on Tuesday night as he picked up a save in Minnesota's 8-6 victory over the White Sox.
"Everything was good," Perkins said. "Everything was fine. I pitched, (and) I didn't think anything of it after the game."
Wednesday morning was a different story.
"When I woke up yesterday I couldn't get out of bed," Perkins said. "It completely blindsided me."
Perkins, who missed a couple of games in late August because of back spasms, is out for an undetermined amount of time with a back strain.