Thielbar (oblique) will start a rehab assignment with Triple-A St. Paul on Tuesday, Do-Hyoung Park of MLB.com reports.
Thielbar has been limited to just one appearance since May 3 due to a pair of injured list stints because of a strained right oblique. He's finally game ready again and should be ready to rejoin the Twins' bullpen following a handful of rehab outings.