Defending champion Samantha Stosur squandered eight match points but finally subdued stubborn British teen prodigy Laura Robson 6-4, 6-4 in 98 minutes to reach the US Open quarter-finals.

Seventh-seeded Stosur advanced to a last-eight meeting with an opponent she has never defeated, world no.1 Victoria Azarenka, of Belarus, who ousted Georgia’s Anna Tatishvili 6-2, 6-2.

Russian third seed Maria Sharapova, the 2006 winner, ousted compatriot Nadia Petrova 6-1, 4-6, 6-4 and now faces Marion Bartoli, who upset Czech left-hander Petra Kvitova, the 2011 Wimbledon winner, 1-6, 6-2, 6-0.

Stosur, Australia’s first women’s Grand Slam champion since 1980, eliminated Robson, the first British woman in the last 16 at the US Open since 1991.

“I’m playing really well,” Stosur said.

“I’m glad to get another match. I’m happy to be into the quarters again.”

Stosur has lost all six career meetings with top seed Azarenka, never taking a set off the reigning Australian Open champion. Azarenka’s most recent victory over Stosur came in last February’s Doha final.

“There’s a few things I’ve learned over those matches that I can put into play and have a much better match and hopefully a very good one,” Stosur said.

“You have to be prepared as soon as you serve, have your game plan and stick to it.”

Robson, 18, had sent Kim Clijsters into retirement and Li Na out of the event in the previous two rounds. But the youngest woman in the world’s top 100 finally faltered under the pressure of the reigning queen of the Flushing Meadows hardcourts.

“I just hit too many unforced errors,” she said.