Dominika Cibulkova downed top seed Victoria Azarenka to pull off a major upset in fourth round action at the French Open yesterday.
The 15th seed won 6-2, 7-6 to set up a quarter-final match with Samantha Stosur who beat Sloane Stephens 7-5 6-4.
Azarenka won the Australian Open in January and had been expected to coast past Cibulkova having beaten her seven times out of eight previously.
But the little Slovak, who reached the semi-finals in 2009, handled the cold, windy conditions far better than the tall Belarusian.
After losing the first set, Azarenka appeared to be getting back on track as she broke to lead 2-0 in the second, but 23-year-old Cibulkova dug deep to run off four games in a row.
Azarenka levelled at 4-4, with the set then going to a tie-break which a pumped-up Cibulkova led from the start to pull off a stunning win.
Earlier Sara Errani, of Italy, and Angelique Kerber, of Germany, both reached the quarter-finals at Roland Garros for the first time with straight sets wins.
Errani, seeded 21, defeated Svetlana Kuznetsova 6-0, 7-5, while 10th seed Kerber ousted Petra Martic 6-3, 7-5.
The pair will meet in the last eight in a top half of the draw which had also contained Azarenka.
Errani has been the form player on clay this year winning tournaments in Acapulco, Barcelona and Budapest.
She also reached the Australian Open quarter-finals in January on hardcourts.
After a tough opening game, Errani took total control as 2009 champion Kuznetsova struggled to put her game together.
The first set was completed in just 30 minutes and it was more of the same at the start of the second as Errani, one of the smaller players on the circuit at just 1.64m, used her mobility and claycourt expertise to good effect.
Errani moved 2-0 up before Kuznetsova finally found some form, breaking the Italian to love to open her account.
The Russian levelled at 2-2 and had a break point in the next game to move ahead, but Errani saved that with a blistering forehand winner at the end of a long rally.
Two more break points followed two games later and Kuznetsova converted the first of these to move 4-3 up. She then served for the set at 5-4 up but was broken to love.
Errani took the next two games to reach her first French Open quarter-finals.