Caroline Wozniacki is in serious danger of losing the world No. 1 ranking ahead of the Australian Open after she was beaten by Agnieszka Radwanska at the quarter-final stage of the Apia International in Sydney.

29030 - Kvitova on brink of ripping No. 1 rank from Wozniacki

Wozniacki will surrender top rank if Petra Kvitova wins the tournament - and the Dane's fate is now out of her hands after she suffered a 3-6 7-5 6-2 defeat. Kvitova, meanwhile, stormed into the semis by hammering Daniela Hantuchova 6-0 6-4.

Wozniacki will be top seed at the Australian Open, which begins on January 16, but Wimbledon 2011 winner Kvitova is now two matches away from landing a significant blow on her rival ahead of the Melbourne tournament.

However, there are doubts over whether Wozniacki will be fit to compete at the year's first grand slam - she required treatment on a wrist injury during her match.

Against Radwanska, Wozniacki claimed a turbulent first set in which there were five breaks of serve: three for Wozniacki, two for her opponent. Neither player was shy to go after a second serve, and it was Wozniacki whose returns proved the more punishing.

Both players shone only intermittently in the second period, with break points coughed up with alarming regularity. Again there were five breaks - and this time it was Radwanska who grabbed three of them to take the set. And she carried that momentum into the third, storming away by dismantling her opponent's serve - in the process totally disrupting Wozniacki's rhythm.

Radwanska now plays Victoria Azarenka, who beat Marion Bartoli 7-5 6-4.

While Wozniacki toiled, Kvitova was peerless: it took until the ninth game of the match for Hantuchova to get on the board, with Kvitova playing superbly in every regard. Early in the second set, Hantuchova had landed with 74% of her first serves - on the face of it, a highly impressive stat - but won just seven of the 23 points contested there. It was a masterclass in returning from Kvitova, whose power was blowing the world No. 21 away.

Hantuchova, who had never beaten Kvitova before the match, restored some pride and fought back to 3-3 with a break - yet it was only a minor blip for Kvitova, who resumed normal service soon afterwards and completed a hugely impressive victory that leaves Wozniacki to fret over her position at the summit of the sport. Kvitova's semi is against Na Li, who beat Lucie Safarova 6-2 7-6(3).