The Royals optioned struggling reliever Brandon Maurer to Triple-A Omaha on Friday afternoon.
In a corresponding move, Kansas City recalled right-hander Kevin McCarthy from Triple-A.
Maurer had a 12.46 ERA and two losses in five appearances this season. In his latest outing, against the Angels on Thursday, the 27-year-old right-hander allowed a three-run triple to Shohei Ohtani and a home run to Mike Trout.
McCarthy had a solid 2017 campaign for the Royals in his second season in the Majors. The 26-year-old made 33 relief appearances and posted a 3.