19 year old American Sloane Stephens, seeded 29, defeated five-time Australian open champion Serena Williams on Wednesday. She beat Serena 3-6 7-5 6-4 to reach the Australian Open semifinals.
Serena had been repeatedly troubled by an ankle injury ever since the beginning of the tournament but still made it this far.
It was Stephens first ever grand slam quarterfinal. Legendary Serena has won a total of 15 grand slam titles.
On Thursday, Sloane Stephens will play her semifinal against defending champion Azarenka who defeated Svetlana Kuznetsova in the quarterfinals.
The second semifinal, on Thursday, will see Li Na take on Maria Sharapova, who is yet to drop at set at the tournament.