"From what the doctors told me after the game and what the trainers told me today, it's just a little tweak," Twins manager Ron Gardenhire said. "It's on his left side from throwing on his follow through. They don't think it's going to be too many days."
Perkins, meanwhile, is dealing with neck stiffness, but an MRI exam on Saturday revealed no structural damage or pinched nerves. Like Santana, Perkins is also expected to return soon.
"We're day-to-day with those two," Gardenhire said.
Schafer, meanwhile, suffered bruised ribs while running into the left-field wall on Friday. He was held of action on Saturday and wasn't in the lineup again on Sunday, but has been cleared to swing a bat.
"Schafer came in today and felt better," Gardenhire said. "He took some swings. And says he's available. Schafer said he feels better and can swing."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.