Twins closer Glen Perkins canceled his Monday bullpen session after feeling discomfort on his right side.
According to the Star Tribune, Perkins was five pitches into his bullpen session when he felt something pull.
"I don't know what it is," Perkins told the Tribune. "It's oblique-ish something. Hopefully it's not bad. It's like a pull more than a strain."
The plan could set Perkins' next appearance on the mound back some; he was scheduled to pitch an inning against the Rays at Hammond Stadium on Wednesday, but that isn't likely to happen now.
Still, the Twins don't seemed overly concerned about it at this point.
Perkins has saved 70 games for the Twins over the last two seasons, including 34 of 41 save opportunities last year.
"On the medical (reports), it isn't anything to be concerned about," Twins general manager Terry Ryan told the Pioneer Press. "He's got a little tweak on his right side around the ribcage so we're going to certainly watch it. I don't think it's anything serious, but he hasn't been out there."
Ryan didn't think it would be too much longer, but added that Perkins wouldn't throw again until "he is right."