Right-handed reliever Jared Burton is expected to see an increased workload in Thielbar's absence, as he's bounced back from his struggles in June. Burton has recorded seven straight scoreless appearances to lower his ERA from 4.29 to 3.59 in 42 2/3 innings.
But right-hander Casey Fien will remain the club's top setup man for closer Glen Perkins, as he's working on a stretch of 10 straight scoreless outings entering Saturday.
"Casey is doing fantastic, and now we're getting stronger with Jared getting back out there," Gardenhire said. "Thielbar has a little bit of a tweaked groin, so we'll have to back off him for a few days. But those three have been throwing really well."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. Kelly Erickson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.