The Royals optioned Klein to Triple-A Omaha on Monday.

Klein struck out two in a scoreless inning Sunday versus the Tigers in what was his major-league debut. He eventually has a chance to play an important role in the Royals bullpen this season, but for now Klein, will head back to Omaha to make room for Monday's starter, Jonathan Bowlan, who was called up from Triple-A in a corresponding move.