The Royals outrighted Black to Triple-A Omaha on Thursday.
The transaction frees a spot on the 40-man roster as the Royals head into the offseeason. Black has made eight starts and 19 relief appearances thus far at the big-league level, logging a 5.53 ERA, 1.62 WHIP and 55:35 K:BB over 71.2 innings. He'll turn 27 in December.