• WTA Tennis

Dizzy Azarenka into Tokyo quarters

Victoria Azarenka required a medical time-out during her win over Roberta Vinci © PA Photos

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• Profile: Victoria Azarenka | Li Na | Maria Sharapova | Sam Stosur | Caroline Wozniacki

Victoria Azarenka overcame a bout of dizziness during her match with Roberta Vinci to book her place in the quarter-finals of the Toray Pan Pacific Open.

The world No. 1 had her blood pressure taken after calling for the trainer midway through the first set, telling the umpire that her head was spinning.

But despite looking flushed throughout the match, Azarenka roused herself to beat the Italian 6-4 6-2 and set up a quarter-final clash with No. 5 seed Angelique Kerber in Tokyo after the German made light work of Urszula Radwanska in a 6-1 6-1 win.

"I arrived a few days before the tournament and really struggled with my health," Azarenka said. "I've been trying to save my energy for my matches.

"I don't know what exactly it is. Hopefully I'll know as soon as possible and get rid of it. I was pretty lucky. I don't know how I got through really."

Maria Sharapova saw off a late rally from Lucie Safarova to book her spot in the quarter-finals with a 6-2 7-6(5) victory. The No. 2 seed, who survived a three-set scare against Britain's Heather Watson in the previous round, looked to be cruising to a routine victory when she opened up a 3-0 lead at the start of the second set.

But Safarova found a way back into the match as Sharapova's unforced errors began stacking up, the Czech breaking back before trading breaks again with the world No. 2.

Safarova might have taken the match into a third set, but Sharapova clung on to reach the last eight in Tokyo, winning the second set tiebreak 7-5. The Russian will face Sam Stosurin the quarter-finals after the Australian edged out Dominika Cibulkova 6-4 7-5.

The Slovak was left to rue nine double faults and converting just one of her break point opportunities as Stosur fired down nine aces of her own to progress in an hour and 36 minutes.

Caroline Wozniacki's return to form continued with a scrappy 4-6 6-3 6-4 victory over China's Li Na, her first win against a player ranked in the top 10 in 2012. The Dane was helped by some wayward hitting from Li in the second set, reverting to her counter-punching game and allowing her opponent to self-destruct at the other end.

Li duly obliged, producing 76 unforced errors to crash out and leave Wozniacki facing Agnieszka Radwanska in the quarter-finals after the Pole brought qualifier Jamie Hampton's run to an end, beating the American 6-4 6-3.

French Open finalist Sara Errani launched a dramatic comeback of her own to oust Marion Bartoli 3-6 6-2 6-2. The Italian, who broke the world's top 10 for the first time earlier in September, saved six break points to deny Bartoli a 2-0 lead at the start of the second set before taking 12 of the next 15 games to secure her quarter-final berth.

Up next for Errani is No. 17 seed Nadia Petrova who was pushed all the way by Petra Martic, firing 15 aces to win a 7-6(2) 6-7(1) 6-4 marathon.

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