Teenager Sloane Stephens announced herself as the new face of American tennis after staging one of the biggest upsets in Australian Open history.
The 19-year-old defeated her idol and five-times champion Serena Williams to reach the semi-finals and a first date with world No 1 and titleholder Victoria Azarenka.
Azarenka earlier overpowered Russian Svetlana Kuznetsova 7-5 6-1.
Stephens, who joked she might now have to replace a picture of Williams on her bedroom wall with one of herself, produced a 3-6 7-5 6-4 win in two hours, 17 minutes.
Underlining the importance of her win is the fact that Stephens is the first American apart from the Williams sisters to reach a grand slam semi-final since Lindsay Davenport in 2005.
Stephens, who went down to Williams in Brisbane recently, said she was determined to win after she found herself trailing a set and a break.
"I was convinced that I was able to do it when I lost serve in the first game in the second set and I went down 2-0," Stephens said.
"And I was like, 'Hmm, this is not the way you want it to happen'.
"From then on, I got aggressive, started coming to the net more and just got a lot more comfortable."
Williams struggled with a back injury and left the court for treatment towards the end of the second set.
The 31-year-old said she was still fighting pain when she returned and thought about retiring from the match for "a nano-second".
But she refused to use her back, which "locked up" after she went for a drop shot in the second set, as a contributing factor in her loss.
"It's fine," Williams said. "You know, just nothing. I think everyone at this stage in the locker room has something wrong with them, so it's fine.
"There's no excuse there. I think my opponent played well and was able to do a really good job."
Azarenka or Stephens will face the winner of today's first semi-final between Russian second seed Maria Sharapova and Chinese sixth seed Li Na, the runners-up of the past two years. AAP