WINSTON-SALEM, North Carolina: 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 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 US 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).

Kvitova, Wozniacki advance

In New Haven, Connecticut, second-seeded Petra Kvitova of the Czech Republic moved into the quarterfinals of the New Haven Open with a 6-2, 6-4 victory over America’s Nicole Gibbs.

The 2011 Wimbledon champion, the only Grand Slam winner in the New Haven field, is coming off a title in Montreal, her first ever in North America, and a run to the semifinals in Cincinnati.

I want to play a lot of matches here, and go for the US Open with a good result,” she said. “I want good matches in my bag.”

Caroline Wozniacki remains undefeated in New Haven after beating Sofia Arvidsson of Sweden 7-6 (4), 6-2 in the second round.

Third-seeded Wozniacki is playing in the tournament for the fifth time and is the four-time defending champion. Wednesday’s victory was her 19th here without a loss.

“I think I just have the same mentality every time I go into a match,” Wozniacki said. “Out of respect for myself, the tournament and the opponent, I treat it as a match that I want to win.”

Her chances for a fifth straight title improved Tuesday when top-seeded Agnieszka Radwanska retired in the second set of a lackluster performance against qualifier Olga Govortsova with a sore shoulder. Radwanska said she did not want to risk aggravating the injury going into the US Open.

The 19-year-old Gibbs was able to come back from 4-1 down to tie Kvitova before world’s fifth-ranked player put her away.

Kvitova will play one of her best friends, Lucie Safarova of the Czech Republic in the quarterfinals. Safarova beat Jie Zheng of China 6-4, 6-0.

Wozniacki had a tougher time in her match. She never trailed against Arvidsson, but dropped three straight games after being up 4-1 in the first set, and had to battle the rest of the way.

“I went a little bit down with my level, she went a little bit up and all of the sudden it was just a struggle to win that first set,” Wozniacki said. “I’m just happy to be through. You don’t always have to be playing your best tennis, but just win the most important points.”

She will play Dominika Cibulkova in the quarterfinals. The 5-foot-3 Slovakian used a powerful forehand to beat Andrea Petkovic of Germany 6-4, 6-1.

Petkovic, who is coming off injuries to her back and right ankle, was playing in her first tournament since April and just her fourth of the year.

Jankovic advances in Texas Open

In Grapevine, Texas, second-seeded Jelena Jankovic advanced to the Texas Open semifinals Thursday night, beating eighth-seeded Sorana Cirstea 6-2, 6-1 in the hard-court tournament.

Jankovic, from Serbia, will face Casey Dellacqua, a 6-4, 6-4 winner over Aleksandra Wozniak.

Third-seeded Roberta Vinci also advanced, topping seventh-seeded Chanelle Scheepers 7-6 (1), 6-2. Vinci will face Bojana Jovanovski.

Jovanovski led sixth-seeded Peng Shuai 6-4, 1-0 when the Chinese player retired because of a right shoulder injury.