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.

Mauer was batting .271 with two home runs and 28 RBI in 76 games before the injury.

Need to stay aggressive

Ryan got excited about starter Kris Johnson's first inning Monday, but wished the lefthander could have maintained that aggressive mentality throughout the outing.

"His first inning was phenomenal," Ryan said. "I was hoping he'd continue it. There's no question he's got plenty of stuff to pitch in this league. And he's lefthanded on top of it, so it's tough to find a lefty with that stuff."

Johnson struck out the side on 16 pitches to start the game, but threw 75 pitches in the next four innings. He allowed three walks and two earned runs in his third start this season.

Ryan said Johnson, 29, didn't attack the strike zone and fell behind in the count during the final four innings of his start

"He needs to get better than that," Ryan said. "He's better than that. So that's what we've decided to do, and we'll bring in another guy for Saturday.

"When he's in sync, his stuff is as good as anybody that we have."

Johnson was optioned to Class AAA Rochester to make room for Tuesday's starter, Yohan Pino. Logan Darnell is expected to be Saturday's starter. The 25-year-old Darnell is 5-5 with a 3.43 ERA in 17 starts with Rochester this season.

Etc.

• Ryan said Class A Fort Myers outfielder Byron Buxton is still day to day after getting hit by a pitch on the right wrist Friday. Ryan said Buxton, the top-rated prospect in the minor leagues according to Baseball America, has started to improve, but the team is being cautious with his latest wrist injury. He already has injured his left wrist twice this season.

• Twins pitcher Ricky Nolasco will have his first bullpen session this weekend as he continues to recover from right elbow soreness, Ryan said.

Ryan did not give a specific date on when that bullpen will happen, and he will leave the pitch count up to Nolasco and pitching coach Rick Anderson.