The Twins activated Thielbar (hamstring) from the 15-day injured list Sunday.

Thielbar (hamstring) gave up a home run with four strikeouts and no walks over two innings Thursday for Triple-A St. Paul. He could be activated from the injured list this weekend, Bobby Nightengale of the Minneapolis Star Tribune reports.

Thielbar (hamstring) will begin a rehab assignment with Triple-A St. Paul on Tuesday, Aaron Gleeman of The Athletic reports.

Thielbar (hamstring) threw a 20-pitch live session Saturday and is progressing towards a rehab assignment with Triple-A St. Paul, Do-Hyoung Park of MLB.com reports.

The Twins placed Thielbar (hamstring) on the 15-day injured list Thursday.

Twins president of baseball operations Derek Falvey said Monday that Thielbar (hamstring) will begin the season on the injured list, Bobby Nightengale of the Minneapolis Star Tribune reports.

Thielbar (hamstring) threw a live batting practice session Saturday, MLB.com reports. "I don't know exact timeline, but I anticipate being just fine for the second half of March at least to get into some games and be ready to go," Thielbar said afterward.

Thielbar is dealing with a left hamstring strain and is throwing a bullpen session Friday, Do-Hyoung Park of MLB.comreports.

The Twins and Thielbar avoided arbitration by agreeing to a one-year, $3.225 million contract Thursday, Kiley McDaniel of ESPN.com reports.

The Twins reinstated Thielbar (oblique) from the 15-day injured list Sunday.