Defending champion Kim Clijsters ended Caroline Wozniacki's reign as world number one when she beat her in straight sets in the Australian Open quarter-finals on Tuesday.
Clijsters held off a determined fight-back from the 21-year-old Dane to win 6-3, 7-6 (7/4) in 1hr 45min and set up a semi-final with third seed Victoria Azarenka.
By failing to reach the semi-finals, Wozniacki is guaranteed to lose her number one ranking to one Azarenka, Petra Kvitova or Maria Sharapova when the new standings are released next Monday.
And the top seed will face inevitable questions over how she managed to hold onto the number one spot for 67 of the last 68 weeks without winning a grand slam.
Wozniacki played her usual counter-punching game on Tuesday with plenty of retrieving from the baseline, but she didn't have a weapon to damage Clijsters.
The Belgian played much better than in her fourth round win over China's Li Na, and showed no ill-effects from the ankle injury she suffered during that match.
Clijsters broke Wozniacki four times in the first set as she dominated her younger rival on both her forehand and backhand sides.
And although Wozniacki broke twice herself, she was always playing catch-up and never looked like taking the set.
The second set followed a similar pattern, but Clijsters faltered while serving for the match at 5-3.
The tiebreak went with serve until 4-4, when Clijsters stepped up to win the next three points and seal victory with a simple put-away into the open court.
"It didn't feel like being up a set and 5-2," the Belgian said. "I really had to work at it. Caroline changed her tactics (in the second set) and became a bit more aggressive."