Justine Henin's 17-match unbeaten run at the Dubai Championships came to an end when she was beaten in the quarter-finals by Italian Francesca Schiavone.
Schiavone beat Henin for the first time in her career
The world number one had won the title on her last four visits to Dubai but put in an erratic display as she lost 7-6 (7-3) 7-6 (7-4).
"She was better, simple as that," said Henin, who had won all seven of her previous matches against Schiavone.
Third seed Ana Ivanovic also went out, beaten 5-7 6-3 6-3 by Elena Dementieva.
Russian Dementieva recorded her third straight win over the Australian Open finalist to book a meeting with Schiavone.
Schiavone looked to have missed her chance when she twice failed to serve out the match in the second set - wasting a match point at 5-4.
But Henin was unable to take advantage, playing a poor tiebreak which Schiavone won 7-4.
"Every point you have to beat her. It's like every point is match point," said Schiavone, whose only previous win over a world number one came against Amelie Mauresmo in the Fed Cup.
"So at the end when I was in the tiebreak I said you push now or you go home, so it's better that you push now. And I did it.
"To beat Justine you have to play very good, at a high level, and I did today. I think for me it is my best win."
Schiavone will meet Ana Ivanovic or Elena Dementieva in the semi-finals.
In the other half of the draw, second seed Svetlana Kuznetsova booked her place in the last four with a 6-1 7-6 win over Amelie Mauresmo.
The Russian's win means Mauresmo still has not won more than three matches in a row since Wimbledon last year.
"I started to play better in the second set and there were times when I played some good tennis," said the Frenchwoman.
"There were still probably a few things here and there which cost me that second set, and I didn't play the tie-break as I expected, but she came up with some good shots when she needed them."
Jelena Jankovic will play Kuznetsova after opponent Anna Chakvetadze retired from their quarter-final.
Jankovic, celebrating her 23rd birthday, took the first set 6-1 before the Russian pulled out with a left thigh injury.