Defending US Open champion Samantha Stosur of Australia and Spanish fourth seed David Ferrer advanced at the US Open with straight-set victories on Friday.
Stosur reached the fourth round with a 7-6 (7/5), 6-2 victory over US 31st seed Varvara Lepchenko while Ferrer moved into the third round by ousting Dutch qualifier Igor Sijsling 6-2, 6-3, 7-6 (14/12).
The 28-year-old seventh seed will next face Chinese ninth seed Li Na or British teen qualifier Laura Robson to decide a spot in the quarter-finals at the year's final Grand Slam event.
Stosur, who has not won a title since lifting the US Open trophy a year ago, avoided the earliest defeat by a defending champion since Maria Sharapova's third-round exit in 2007.
Uzbek-born lefthander Lepchenko, who became a US citizen a year ago, has never beaten a top-10 player. She was trying to match her best Grand Slam result, this year's fourth-round French Open run.
After an exchange of service breaks in the first two games, both Lepchenko and Stosur held into a tie-breaker that went to 5-5 before Lepchenko sent a lob and a backhand wide to surrender the opening set after 59 minutes.
Stosur broke Lepchenko in the third and fifth games of the second set and held to finish the match after 88 minutes.
"It was a little windy," Stosur said. "Every now and again it gusts up. It just takes a while to get used to it but once I did I was able to get it going."
Ferrer, a 2007 US Open semi-finalist in his best Grand Slam run, battled through five match points and denied the Dutchman on three set points in the tie-break before a lob winner and a victory after two hours and seven minutes when Sijsling netted a forehand.
"He played very well in the third set," Ferrer said. "I was pleased to get it done."
French 11th seed Marion Bartoli also advanced with a 6-2, 6-4 victory over compatriot Kristina Mladenovic.
Defending men's champion Novak Djokovic will face Brazil's Rogerio Dutra Silva later as the second-seeded Serb bids for a spot in the third round.
And Andy Roddick, the 2003 US Open champion who announced Thursday that this would be the final event of his career, later tries to keep his career going into the weekend, the US 20th seed facing Australian Bernard Tomic.
Third-seeded Russian Maria Sharapova, the reigning French Open champion, meets US wildcard Mallory Burdette and Belarus top seed Victoria Azarenka, the reigning Australian Open champion, plays China's Zheng Jie in later women's matches at Arthur Ashe Stadium.