|Stosur stunned the world no1 despite a fightback in Paris [GALLO/GETTY]
Serena Williams became the latest champion to fall at Roland Garros but Rafael Nadal proved rock-solid by staying on course to regain his French Open title.
The day after defending champion Roger Federer's hopes were shattered by Robin Soderling, Williams suffered a quarter-final defeat, losing a three-set cliffhanger to Australia's Samantha Stosur after squandering a match point.
Novak Djokovic, the former Australian Open champion, suffered a similar fate when the men's third seed blew a two-set lead against journeyman Jurgen Melzer of Austria.
It was the fall of world number one Williams that made the biggest impact, however, as she had seemed to be closing in on a 13th Grand Slam title and her first in Paris since 2002.
The American amazingly lost 17 consecutive points midway through her match with Stosur but still came back fighting and but for a forehand that missed by less than a ball's width she would have survived to fight another day.
As it was, steely seventh seed Stosur stayed the course to win 6-2 6-7 8-6 as some Gold Coast-like sunshine finally returned to illuminate Court Philippe Chatrier after most of the claycourt slam had unfolded under grey skies and drizzle.
It was a first victory against a current world number one for Stosur, who stunned four-times champion Justine Henin in round four, while for Williams it was her first Grand Slam defeat having held matchpoint since the 1999 Australian Open.
Her loss meant only one of the top four women's seeds reached the semi-finals, that being Serbia's Jelena Jankovic who prevailed 7-5 6-4 against Kazakhstan's unseeded Yaroslava Shvedova to seal a clash against Stosur.
With Russia's Elena Dementieva and Italy's Francesca Schiavone contesting the other women's semi-final on Thursday, one thing is certain – this year's French Open will have a first-time Grand Slam champion.
With Federer in search of grass courts and Djokovic out of the way, Nadal's route to re-take his title and the world number one spot looks enticing, although danger lurks in the form of Soderling, still the only man to beat Nadal in 37 matches at Roland Garros.
Nadal earned a 7-6 7-6 6-4 victory against a pugnacious opponent who went toe-to-toe with the four-times champion in a high-intensity baseline battle.
"I'm very happy how I played the tiebreaks. I played aggressive, very focused, and in the important moments I think I played better than the rest of the match," Nadal, who has now won 22 consecutive matches against fellow Spaniards, told reporters.
Match of the day was staged on Court Suzanne Lenglen where Djokovic and Melzer grafted for more than four hours.
Djokovic looked razor-sharp when broke to lead 2-0 in the third after bossing the opening two sets but the wheels fell off and Melzer played the match of his life to win 3-6 2-6 6-2 7-6 6-4 and become the first Austrian since Thomas Muster in 1995 to reach the last four of the French Open.