Ivanovic hopes to be fit to play in Dubai next week

Poland's Agnieszka Radwanska was handed a walk-over into the quarter-finals after Ivanovic pulled out.

Wimbledon champion Venus Williams lost 6-3 6-3 to Dominika Cibulkova, while second seed Svetlana Kuznetsova lost 6-3 7-6 (10-8) to Sybille Bammer.

But third seed Jelena Jankovic and fourth seed Maria Sharapova progressed.

Jankovic beat Ai Sugiyama of Japan 6-1 6-2, while Sharapova saw off Thailand's Tamarine Tanasugarn 6-2 6-2.

When I was little she was one of my idols, so I still can't believe it Dominika Cibulkova on beating Venus Williams

Bammer will meet Vera Zvonareva, who accounted for fellow Russian Dinara Safina 7-5 6-3, in the last eight.

Next up for Jankovic is Li Na, who thumped 12th seed Shahar Peer 6-1 6-3, while Sharapova faces Denmark's Caroline Wozniakci.

"I played her in an exhibition match sometime back," Sharapova said of Wozniakci.

"She is an upcoming player and it should be a good match."

Serbian Ivanovic had damaged her left ankle when she slipped over on the baseline just four points before beating Olga Govortsova 6-3 6-1 on Wednesday.

However, she is hopeful of making next week's Dubai Open.

"The injury is not as bad as I thought. There is no fracture, it's an ankle sprain," said the world number three.

"But it is pretty painful and it is hard to step on it.

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"I am definitely very disappointed. It's a disappointing way to end the tournament and I thought I was in good shape.

"Conditions were tough but I was happy with my game and I though I was playing well. I thought I was in with a chance of another title."

Williams made 40 unforced errors as she tumbled to defeat against Cibulkova, compared to just four by her 18-year-old Slovak opponent.

A delighted Cibulkova, who had never beaten a player ranked in the top 20 in the world before this week, said: "When I was little she was one of my idols, so I still can't believe it.