Two women in reach of the tennis world number one ranking, Maria Sharapova and Petra Kvitova, will both take on unseeded opponents in the Australian Open quarter-finals today.
Fourth seed Sharapova, who won the Open in 2008, will meet fellow Russian Ekaterina Makarova, who beat US star Serena Williams in straight sets in the previous round.
Second-seeded Czech Kvitova will meet Italian Sara Errani.
Sharapova, Kvitova and Belarusian Victoria Azarenka are all battling for the number one spot, which will be vacated by Caroline Wozniacki after her quarter-final exit yesterday.
Wozniacki was ousted by reigning champion Kim Clijsters, who will meet third seed Azarenka in the first semi-final.
Meanwhile Long-time rivals Roger Federer and Rafael Nadal will meet in the first men's semi-final, with the make-up of the other men's semi-final to be decided today.
British hope Andy Murray, the fourth seed and losing finalist of the past two years, will take on Japan's 24th seed Kei Nishikori in one quarter-final.
Then world number one Novak Djokovic, who defeated Australia's last hope Lleyton Hewitt in four sets in the fourth round, will meet Spanish fifth seed David Ferrer in the other in the feature night match tonight.
