The Marlins optioned Kempner to Triple-A Jacksonville on Wednesday, Christina De Nicola of MLB.com reports.
Kempner was summoned Tuesday from the minors and made his major-league debut in Miami's 9-7 loss to Baltimore with a perfect inning out of the bullpen. He'll make room on the roster for a fresh bullpen arm in Dax Fulton, who was called up from Jacksonville in a corresponding move.