China's 18th-seeded Wang Qiang advanced to the US Open quarter-finals on Sunday with a 6-2, 6-4 upset of Australian second seed Ashleigh Barty, the reigning French Open champion. Wang will face the winner of a later fourth-round match between Croatian 22nd seed Petra Martic and US eighth seed Serena Williams, who is seeking a 24th career Grand Slam title to match Margaret Court's all-time record.

Wang was unsure if she would watch the Williams-Martic match, leaving that duty to her coach, Thomas Drouet. "I think that's my coach's homework," Wang said. "I just want to enjoy now and my coach will tell me how to play next." Wang's previous coach had been Peter McNamara, who died in July of prostate cancer.

Barty, who beat Wang twice last year in their only prior meetings, was undone by 39 unforced errors while Wang made only 14.

Copyright Agence France-Presse, 2019