Winston-Salem, NC (Sports Network) - Top seed Jo-Wilfried Tsonga, former Wimbledon runner-up Tomas Berdych and defending champion John Isner posted third-round wins Wednesday at the $550,000 Winston-Salem Open, a final U.S. Open tune-up.
Tsonga beat Ukraine's Sergiy Stakhovsky 7-6 (7-1), 6-4 on the hardcourts at Wake Forest University.
Next up for the Frenchman is sixth-seeded Spaniard Marcel Granollers, who rallied past Latvian qualifier Ernests Gulbis 4-6, 6-3, 6-2.
The second-seeded Berdych handled 16th-seeded Finnish veteran Jarkko Nieminen 6-3, 6-2.
Capable Belgian Steve Darcis drove out fifth-seeded American Andy Roddick in a pair of tiebreaks, 7-6 (8-6), 7-6 (7-3).
The former world No. 1 and former U.S. Open champion Roddick lost early at last week's Masters event in Cincinnati, where he was slowed by back problems. He's now dropped three of his last four matches after winning five straight, including a hardcourt title in Atlanta.
Darcis will do battle with Berdych in the quarterfinals.
Isner, the No. 3 seed, dispatched 13th-seeded Austrian Jurgen Melzer 6-4, 6-3.
The North Carolina native Isner beat Frenchman Julien Benneteau in last year's Winston-Salem finale.
David Goffin outlasted Lukasz Kubot 6-3, 1-6, 7-6 (7-5) and will take on Isner in the quarters.
Meanwhile, fourth-seeded Alexandr Dolgopolov of Ukraine moved into the quarterfinals with a 6-3, 6-4 decision against 14th-seeded Argentine David Nalbandian.
Seventh-seeded American Sam Querrey, who currently leads the U.S. Open Series standings, continued his fine summer with a 6-3, 6-4 victory over ninth-seeded Spaniard Feliciano Lopez on Day 4. Querrey will meet Dolgopolov in the round of eight on Thursday.
The 2012 Winston-Salem champion will collect $73,930.