American teenager Sloane Stephens sent the Australian Open women's draw into disarray Wednesday when she dumped injury-hit hot favourite Serena Williams out of the quarter-finals.
Stephens, only 19 and without a tournament victory, held her nerve in almost unbearable tension at Rod Laver Arena to close out a 3-6, 7-5, 6-4 win after Williams needed treatment for back spasms.
"This is so crazy," said Stephens, who used to have a poster of Williams on her bedroom wall. "I think I'll put a poster of myself up now."
Stephens, 19, regarded as Williams' successor as the force of women's tennis in the United States, now goes into a semi-final against world number one and defending champion Victoria Azarenka, who beat Svetlana Kuznetsova.
US Open champion Andy Murray, bidding to become the only man ever to win his first two Grand Slam titles back-to-back, beat Jeremy Chardy 6-4, 6-1, 6-2 to set up a semi-final against Roger Federer or Jo-Wilfried Tsonga.
Williams, 31, had not been beaten since August and picked up titles at Wimbledon, the Olympics and the US Open last year, but she now sees her bid for a calendar-year Grand Slam falter at the first hurdle.
She also falls one short match of equalling her best-ever winning streak of 21 matches, and is denied the chance to become the oldest world number one since computer rankings were first devised in 1975.
But she said she was "almost relieved" her tournament was over after rolling her ankle just minutes into her first match in Melbourne, a problem which she believes had the knock-on effect of straining her back.
"Absolutely," she said, when asked if it was the worst time she had had at a Grand Slam.
"Oh, my gosh, I'm almost relieved that it's over because there's only so much I felt I could do... oh my gosh, it's been a little difficult. I've been thrown a lot of balls these two weeks."
Williams won the first set but at 3-4 in the second, she pulled up with back spasms and later called for the trainer. As she served at half-pace, Stephens was eventually able to capitalise as she levelled at a set each.
Williams recovered sufficiently to break in the tense decider but Stephens broke back and then broke again to claim the victory of her life.
"Today I just really didn't have anything to lose. I mean, you're playing for the semis of a Grand Slam. You just got to go out and do it really," Stephens said.
In Thursday's semi-finals Stephens will face top seed Azarenka, who came through a marathon, 1hr 17min opening set against resurgent Russian veteran Kuznetsova before completing her 7-5, 6-1 triumph in 1hr 47min.
"She played really well throughout the whole match," Azarenka said. "At the beginning, it took adjustment because she plays such a different game.
"I'm glad I fought through and produced my best tennis when it was needed."
Murray produced his best performance of the men's tournament so far to send unseeded Frenchman Chardy spinning out.
Murray broke Chardy's service eight times and played a clean match with 32 winners against 20 unforced errors, as he extended his Grand Slam winning streak to 12 matches and reached his 12th major semi-final.
"Today was the best I've played. I've struggled in my last few rounds a little bit, my last opponent (Gilles Simon) was injured so it wasn't much of a match as he struggled physically," Murray said.
"Jeremy's had a great tournament, he's beat some top players so I needed to come out sharp and get off to a good start.
Four-time champion Federer was due to play Tsonga, the 2008 runner-up, in the evening match on Rod Laver Arena.