The Twins activated Thielbar (hamstring) from the 15-day injured list Sunday.
Thielbar opened the season on the injured list with a hamstring strain but is ready to join the big club after two rehab appearances with Triple-A St. Paul. The left-hander recorded 14 holds and had a 3.23 ERA, 0.95 WHIP and 36:6 K:BB across 30.2 innings last season, and he should fill a high-leverage role for the Twins now that he's healthy.