Thielbar left Wednesday's game against the Orioles in the seventh inning with a strained groin, Do-Hyoung Park of MLB.com reports.
Manager Rocco Baldelli said the team will decide within a day whether they'll place Thielbar on the injured list. Regardless, the lefty will require some time off to recover from the injury, putting further strain on what's been an overworked bullpen of late amidst multiple injuries in the Twins' starting rotation.