Cuas was called up from Triple-A Omaha on Tuesday.
Cuas will return to the big leagues after being sent down Aug. 2. The right-hander has produced a 3.18 ERA and 1.54 WHIP with 19 strikeouts over 22.2 innings in 27 appearances with the Royals this year. He'll replace Taylor Clarke (oblique) in the bullpen after Clarke was placed on the 15-day injured list Tuesday.