World No.1 Victoria Azarenka has crashed out of the French Open in a major boost to Samantha Stosur’s title hopes.

Azarenka slumped to a shock 6-2 7-6 (7-4) fourth-round loss to Slovakian 15th seed Dominika Cibulkova on Sunday, handing Stosur a big opportunity to seize on a wide open draw.

Australia’s 2010 runner-up plays unseeded American teenager Sloane Stephens later on Sunday, with the winner to face Cibulkova in the quarter-finals – instead of Azarenka.

Stosur has lost all six career encounters with Azarenka, never even taking a set off the Belarussian, who ascended to the top of the rankings after her Australian Open triumph in January.

The other quarter-final in Stosur’s bottom half of the draw has already been decided, with Italian 21st seed Sara Errani to take on German 10th seed Angelique Kerber.

Errani defeated Russia’s 2009 Roland Garros champion Svetlana Kuznetsova 6-0 7-5 in her fourth-round match, while Kerber ousted Croatian Petra Martic 6-3 7-5.

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 on hard courts.