The Royals optioned Waters to Triple-A Omaha on Sunday.
The move is to make room on the 26-man roster for MJ Melendez (ankle), who was reinstated off the 10-day injured list. Waters made four appearances for the Royals after being recalled July 18, going 2-for-8 with one RBI, two runs scored and two walks. In Triple-A this season, Waters is slashing .277/.362/.502 with 10 home runs, 44 RBI and 11 stolen bases across 287 plate appearances.