Williams upset by disappointing display

Serena Williams struggled 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.

"It was my match and I lost it. That's basically what happened," said 2002 champion Williams, who cut a frustrated figure for much of the contest.

For 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.

"I didn't play well, I don't think at all, from literally the first point," she added. "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."

Stosur, who lost to eventual champion Svetlana Kuznetsova in last year's semis, will now play Jelena Jankovic 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. I didn't know if I was going to get another chance.

"That third set, I just kind of hung in there, and I was behind the whole time serving second. I just tried to hang in and wait for another opportunity. Then I got one at 6-6, and thankfully I took it."