Mercedes knocked in Luis Robert with a double in the seventh inning to break a 6-all tie. The big night helped the Sox (10-9) get over .500 for the first time this season.
Adam Eaton had a two-run double and scored on a Yoán Moncada single. Mercedes drove in two with a single, extending the lead to 5-0. Dunning, who was traded to the Rangers in the offseason as part of the deal for starter Lance Lynn, exited after surrendering a single to Andrew Vaughn.
Dunning allowed five runs on eight hits with two strikeouts and two walks in 2u2154 innings.