Thielbar was placed on the 15-day injured list with a left hamstring strain Saturday, retroactive to July 19, Brandon Warne of Access Twins reports.
Thielbar was effective prior to the All-Star break, allowing two hits and two walks while striking out six in 4.1 scoreless innings over his last four appearances. However, he's dealing with a hamstring issue that will keep him out until at least early August. Yennier Cano was recalled from Triple-A St. Paul to take Thielbar's place in the bullpen.