MINNEAPOLIS -- Twins right-hander Kevin Slowey has a strained right biceps muscle, and it's uncertain exactly when he'll be able to make his next start.

Slowey left his start on Thursday against the Angels with one out in the fourth inning after feeling tightness in the front of his right arm.

Twins manager Ron Gardenhire said they had noticed during the outing that the Slowey kept shaking his arm. After seeing him do it once again early in the fourth, Gardenhire and trainer Rick McWane went to the mound to check on him. The meeting came just after Slowey had retired former Twins center fielder Torii Hunter on a groundout to third base.

"He said, 'I'm tight,' and I said, 'You're out," Gardenhire said. "We're going to take care of this young man's arm. He has a good future here, and we want to keep it that way."

Afterward, Slowey couldn't pinpoint exactly when the injury first occurred. He said the doctors told him it could have happened on one pitch or it could have been building. Slowey didn't know which it was.

"It just feels tight and like I can't really finish pitches, which isn't really conducive to getting outs," Slowey said.

The pitcher said the team doctors told him the strain was nothing serious, but something the club would be cautious with for now.

Slowey will be re-evaluated on Friday. So far, no MRI has been scheduled.

How long Slowey will be sidelined with the injury won't be known until the next few days, Gardenhire said. The skipper indicated that the team likely will use its off-day on Tuesday to skip Slowey's next start and allow the pitcher a few extra days to heal.

If Slowey's injury requires a stint on the disabled list and the team needs to call up another starter, Gardenhire said it won't necessarily be left-hander Francisco Liriano, who is scheduled to make the first of two Minor League starts on Thursday night.

"We will not adjust his schedule because of something that happens up here," Gardenhire said of Liriano. "Liriano is on schedule, and he's going to do what we set out to do, and we will not make any adjustments. Only when Liriano's ready, and that's a couple of starts, at least."