Leahy was optioned to Triple-A Memphis on Saturday.
Leahy made his big-league debut in early July but allowed at least one run in all three of his relief appearances, failing to record three outs in any of them. He'll take his 21.60 ERA and 5.40 WHIP back to the minors, with Drew VerHagen (hip) returning from the injured list to take his spot in the bullpen.