BEIJING (Reuters) - Top seed Ana Ivanovic of Serbia withdrew from the Olympic tennis event on Sunday with an injury to her right thumb.
"This is one of the hardest moments of my career and one of the hardest decisions I've had to take," 20-year-old Ivanovic told a news conference at the Olympic Tennis Centre.
"I was so looking forward to playing here and being part of this occasion."
Ivanovic, who will be replaced by fellow Serb Jelena Jankovic at the top of the world rankings on Monday, said she had not been able to practise since arriving in China.
The French Open champion was due to play Mariya Koryttseva of Ukraine in the first round but said she would go home "in a day or two" to try to recover in time for the U.S. Open.
Ivanovic said she suffered the injury when she returned to practice following a two-week break after her disappointing showing at Wimbledon where she lost in the third round.
"I've tried everything to recover and I've had more treatments in 10 days than I've had in my life," she said.
"I tried to play in Montreal and get some matches but it was so painful I went back to get some more treatment.
"I decided to come here and try to practise but it was too painful. I haven't played at all in the last 10 days.
" ... This kind of injury takes time and unfortunately I didn't have that."
The injury, which Ivanovic described as inflammation of the carpal-metacarpal joint, casts doubt over her participation at the U.S Open which starts later this month.
"It's too early to say," she said. "I don't want to get my hopes too high because I only have two weeks to recover. It's really frustrating. We will talk to the doctors again and see what the best thing is to do."
Ivanovic joins a growing list of players who have pulled out of the Olympic tennis event. Maria Sharapova withdrew with a shoulder injury and Lindsay Davenport pulled out of the singles on Friday with a knee injury.
In the men's draw Croatians Ivo Karlovic and Ivan Ljubicic both withdrew injured from the singles on Saturday.
(Editing by Alison Williams)