Juan Martin del Potro returns from break to win

Juan Martin del Potro opened his summer hard-court season with a 7-5, 6-3 victory over American Marcos Giron on Wednesday night in the Mifel Open.

Playing for the first time since losing to Rafael Nadal in the Wimbledon quarterfinals, the top-seeded del Potro set up a quarterfinal match against Egor Gerasimov.

Del Potro won hard-court titles this year at Indian Wells and Acapulco. The fourth-ranked Argentine star has 22 career victories, the biggest on a hard court in the 2009 U.S. Open.

Gerasimov, from Belarus, outlasted fifth-seeded defending champion Sam Querrey of the United States 7-5, 5-7, 7-6 (6). Querrey swept the Los Cabos and Acapulco events last year.

Fourth-seeded Adrian Mannarino of France topped Sweden's Elias Ymer 6-0, 6-2. The Frenchman will play Cameron Norrie, the British left-hander coming off a semifinal appearance in Atlanta. Norrie beat eighth-seded Feliciano Lopez of Spain 6-3, 6-3.

Japan's Yoshihito Nishioka also knocked off a seeded player, topping seventh-seeded Taylor Fritz of the United States 7-6 (3), 6-1. Nishioka will face second-seeded Fabio Fognini of Italy.

Third-seeded Damir Dzumhur of Bosnia and Herzegovina got past Italy's Thomas Fabbiano, 7-6 (0), 7-6 (5). He'll play American Michael Mmoh, a 7-6 (1), 7-6 (2) winner over Canada's Peter Polansky.