The Orioles recalled Mayo from Triple-A Norfolk, and he will start at third base and bat sixth Sunday against the Rockies.
The 22-year-old has joined the Orioles with MLB active rosters expanding to 28 players Sunday, and placement of Ramon Urias (ankle) on the injured list could open up everyday playing time for Mayo at third base. Mayo struggled in his first taste of the majors, going 1-for-17 with 10 strikeouts over his first seven games, but he appears poised to get plenty of chances in September while Urias is sidelined.