Busenitz was optioned to Triple-A Rochester, Mike Berardino of the St. Paul Pioneer Press reports.
Busenitz struggled this spring (7.27 ERA) but this is still a surprise since he was seen as almost a lock to make the bullpen when spring began. He'll likely be called up early in the season as the Twins may aggressively rotate the back end of their bullpen between Triple-A and the majors.