Serena Williams is struggling to comprehend how she could have played so badly after becoming the second modern great to fall to Samantha Stosur at this year's French Open.
Seventh seed Stosur, who on Monday became the first woman to beat Justine Henin at Roland Garros for six years, held off a tremendous fightback by Williams — who had match point — to win 6-2 6-7 (2/7) 8-6 and reach her second successive Roland Garros semi-final.
The Australian made full use of her impressive physique to overpower world number one Williams for almost two sets but looked to have blown her chance after serving for the match in the second.
Yet she held her nerve in a dramatic decider to win in two hours 24 minutes on Philippe Chatrier Court.
For 2002 champion Williams, it was another quarter-final defeat at the French Open, which she had been a strong favourite to win being the only grand slam champion left in the draw.
“It was my match and I lost it. That's basically what happened,” said the 28-year-old, who cut a frustrated figure for much of the contest.
“I didn't play well, I don't think at all, from literally the first point.
“I was more or less upset that I was able to play so well up until this point, and then I didn't believe that it was over.
“I just couldn't believe that I played like that.”
Williams, who brushed Stosur aside en route to the Australian Open title in January, showed her renowned fighting spirit to level at one set all and fashion a match point in the decider.
Stosur, who lost to eventual champion Svetlana Kuznetsova in last year's semis, will now play Jelena Jankovic today for a place in Saturday's final.
The 26-year-old has been a revelation in the past year after finally recovering from the debilitating effects of Lyme disease which practically sidelined her for nine months until 2008.
Stosur revealed afterwards her thoughts turned to a previous match against Williams — in which she had blown four match points — during the deciding set.
“It's good to know that I've learnt from that situation, and this time didn't let it happen,” she said, admitting she feared she might not get another chance after failing to serve out the match in the second set. “After losing that game, things kind of stepped up a notch from her,” she said.
Rafael Nadal shook off dogged resistance from Nicolas Almagro to stay on course for a fifth French Open title.
Although he maintained his record of not having dropped a set at this year's tournament, the world number two was made to fight all the way by his fellow Spaniard before sealing a 7-6 (7/2) 7-6 (7/3) 6-4 victory.
Jurgen Melzer came from two sets down to beat number three seed Novak Djokovic. After four hours and 15 minutes of intense battle, No. 22 seed Melzer eventually triumphed 3-6 2-6 6-2 7-6 (7-3) 6-4.