Anthony Swarzak will start for Kyle Gibson, who was scratched because of lower back stiffness, on Wednesday.
"I cannot elaborate on that," manager Ron Gardenhire said after Tuesday's 8-2 loss to the Indians. "That's exactly what I was told by the doctors. If you see him out there, you'll see why. He can't move."
Gardenhire said Gibson dealt with tightness during or after his bullpen session to the point where his back locked up and needed treatment.
Swarzak, who found out just after the game that he would start, is 1-0 with a 4.34 ERA in 30 appearances this season. He hasn't started since Oct. 2, 2012.
"I'm ready; I've been waiting for an opportunity to start," Swarzak said. "This is a necessity thing with the organization needing a guy to start tomorrow. I didn't pitch tonight, and I'll always take that ball.
Next steps
First baseman Joe Mauer took full swings off a tee in the batting cages before Tuesday's game in his recovery from a strained right oblique. General Manager Terry Ryan said Mauer is making strides to returning with soft toss in the batting cages as the next step.
Mauer missed his 17th game Tuesday since being placed on the disabled list July 2. He was eligible to return after the All-Star break, but his recovery hasn't progressed as expected.
"Until he takes a complete batting practice in that cage, then we'll start getting serious about what his next steps are," Ryan said.