Maria Sharapova reached the US Open quarterfinals for the first time since her 2006 championship run with a 6-1, 4-6, 6-4 victory over Russian compatriot Nadia Petrova on Sunday.
And defending champion Samantha Stosur of Australia set up a last-eight showdown with top seed Victoria Azarenka as both captured fourth-round triumphs on the Flushing Meadows hardcourts at the year's last Grand Slam tournament.
Third seed Sharapova, who completed a career Grand Slam by capturing the French Open title last June, rallied after twice dropping four games in a row and having to sit through a 73-minute rain delay.
"I'm so happy to be in the quarters," Sharapova said. "It has been so many years and it's a great stage to be at."
Seventh seed Stosur squandered eight match points but finally subdued stubborn British teen prodigy Laura Robson 6-4, 6-4 in 98 minutes.
She advanced to a quarter-final against an opponent she has never defeated, World No. 1 Azarenka of Belarus, who ousted Georgia's Anna Tatishvili 6-2, 6-2, to reach her first US Open quarter-final.
"As defending champion she's going to be really motivated. I'm motivated as well," Azarenka said. "It's my first quarter-final at the US Open and I'm really looking forward to it."
Sharapova will next face French 11th seed Marion Bartoli, who beat Czech fifth seed Petra Kvitova, the 2011 Wimbledon winner, 1-6, 6-2, 6-0, to book her first trip to the US Open quarterfinals at her 11th attempt.