WINSTON-SALEM, N.C. (AP) - Defending champion John Isner overcame two rain delays to advance in straight sets, while Andy Roddick was eliminated from the Winston-Salem Open on Wednesday.

The third-seeded Isner, ranked 10th in the world, needed only 71 minutes to beat 13th-seeded Jurgen Melzer of Austria 6-4, 6-3 in the third round at the Wake Forest Tennis Complex.

The fifth-seeded Roddick, a former world No. 1 player now ranked 21st, fell to 81st-ranked Steve Darcis of Belgium 7-6 (8-6), 7-6 (7-3), in the final hard-court tournament before the U.S. Open next week in New York.

Top-seeded Jo-Wilfried Tsonga of France also advanced to the quarterfinals along with second-seeded Tomas Berdych of the Czech Republic, fourth-seeded Alexandr Dolgopolov of the Ukraine, sixth-seeded Marcel Granollers of Spain, seventh-seeded Sam Querrey and Belgium's David Goffin.

Tsonga defeated Sergiy Stakhowsky of the Ukraine 7-6 (7-1), 6-4; Berdych downed Finland's Jarkko Nieminen 6-3, 6-2; Dolgopolov beat No. 14 David Nalbandian of Argentina 6-3, 6-4; Granollers rallied to beat Latvia's Ernests Gulbis 4-6, 6-3, 6-2; Querrey edged ninth-seeded Feliciano Lopez of Spain 6-3, 6-4; and Goffin downed Poland's Lukasz Kubot 6-3, 1-6, 7-6 (7-5).