Kansas City remained four games behind Baltimore in the American League Wild Card race.
Merrifield's double scored speedsters Terrance Gore and Jarrod Dyson, who were running on the pitch. And it gave rookie Kevin McCarthy, who recorded the final out of the sixth, his first Major League win.
The Royals got a scare when closer Wade Davis ran into trouble in the ninth and the White Sox had the potential tying run on third with one out.