- Maria Sharapova pulls out of the Pan Pacific Open in Japan after twisting her ankle
- She was losing 4-3 in the first set of her quarterfinal match against Petra Kvitova
- World number one Novak Djokovic also announced he was pulling out of the China Open due to injury
- Players had threatened a strike due to tournament 'burn out'
World number two Maria Sharapova limped out of the Pan Pacific Open in Tokyo after twisting her ankle during her quarterfinal match against Petra Kvitova of the Czech Republic.
Sharapova had hoped for revenge after the Kvitova beat her in the final at Wimbledon this year.
But with Sharapova losing 4-3 in the first set the Russian fell and retired shortly after.
"I hit a serve and then landed awkwardly on my left ankle. I felt a sharp pain and next thing I knew I was on the floor. It swelled up immediately and I knew there was no way I could continue," Sharapova said in a statement quoted by AFP.
"I am incredibly disappointed and in a lot of pain. I obviously really wanted to win and felt that I was playing well."
Sharapova's retirement means that Kvitova will now face another Russian, Vera Zvonareva, in the semifinals although the Czech player expressed her sadness at the manner in which the match ended.
"We played very nice tennis, I think, and it was a great match," she told AFP.
"I'm very sorry about her, because the ankle swollen was too big straight away. Hopefully... she will be back early."
Victoria Azarenka of Belarus and Agnieszka Radwanska of Poland will contest the other semifinal.
But it was a day when injuries ruled the headlines after Novak Djokovic also pulled out of a tournament due to injury.
The Serbian player, ranked number one in the world after his stunning U.S. Open triumph earlier this month, announced he was pulling out of the China Open after injuring himself in a recent Davis Cup match.
The injury has also put Djokovic's appearance in next month's Shanghai Masters in doubt. World number three Roger Federer and Frenchman Richard Gasquet have already pulled out of the event.
The injuries come at the end of a grueling season where several top players have raised the prospect of a strike over the amount of tennis being played.