Melzer and Stosur leave Nadal as the last former Slam winner standing

Rafael Nadal will be the only semi-finalist in either singles competition to have won a Grand Slam title after another day of drama here at the French Open yesterday. While the Spaniard remained on course to win his fifth Roland Garros title, Novak Djokovic lost a four-hour thriller to Jurgen Melzer and Serena Williams, the world No 1, was beaten by Samantha Stosur.

Djokovic, the world No 3, looked to be in command after winning the first two sets, but Melzer, playing in his first Grand Slam quarter-final, staged a remarkable recovery to win 3-6, 2-6, 6-2, 7-6, 6-4. The 29-year-old Austrian, who had never previously won a match from two sets down, raised his game in the latter stages as Djokovic saved 20 break points.

The world No 27 broke at 4-4 in the decider but wobbled as he served out for the match. At 0-15 Djokovic thought he had hit a winner, only for the umpire, Carlos Bernardes, to rule that the ball was out. Djokovic's protests were to no avail – he said the umpire's ruling was "unbelievable" – and Melzer went on to hit a service winner on his third match point, having fluffed his first by netting the simplest of volleys.

In the semi-finals Melzer will face a fellow left-hander in Nadal, who progressed despite stern resistance from Nicolas Almagro, 7-6, 7-6, 6-4 after two hours and 35 minutes. Robin Soderling meets Tomas Berdych in tomorrow's other semi-final.

Williams, who has not reached the final here since her only French Open victory in 2002, lost 6-2, 6-7, 8-6 to an opponent who must have wondered three years ago whether she would ever realise her potential. Stosur had reached the world's top 30 before being struck down in 2007 by Lyme Disease, which kept her off the court for seven months and threatened her career.

When the 26-year-old returned in 2008 she was ranked outside the world's top 150 and was playing minor tournaments on the International Tennis Federation circuit. However, this was the second year in succession that she has reached the semi-finals here.

If the draw was kind 12 months ago, nobody could deny the world No 7 her right to be in the last four this time around. Having already beaten Justine Henin, the four-times champion, Stosur had to overcome a typically gutsy performance by Williams, who failed to convert a match point at 5-4 in the final set. It was the first time the American had lost a Grand Slam match after having a match point for 11 years.

Stosur now plays Jelena Jankovic after the Serb's 7-5, 6-4 victory over Yaroslava Shvedova. Elena Dementieva faces Francesca Schiavone in the other semi-final.