Andrea Petkovic continued her excellent run in grand slams in 2011 by defeating Carla Suarez Navarro to reach the last eight at Flushing Meadows.
The 10th seed became the first woman to reach the quarter-finals at three slams this season with a comfortable 6-1 6-4 victory.
German Petkovic, who had been unsure whether she would even play at Flushing Meadows because of a knee injury, emulated her runs at the Australian and French Opens to set up a last-eight showdown with world number one Caroline Wozniacki.
Confidence
Petkovic credited her performance in New York last year for her form this season, saying: "I think after last year's breakthrough here, when I reached fourth round, my confidence changed completely.
"I just started believing in myself that I could reach the second weeks of grand slams. Before, I was just playing and seeing what happens.
"And now, after that, I really started believing in myself and I started focusing also and putting my plan as if I'm going to play for two weeks. That has changed."
