Ana Ivanovic is optimistic about defending her French Open title, saying that a niggling knee injury had died down.

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"Thankfully the pain and inflammation in my knee has gone away so I have been able to practise this week," the Serbian said, despite an earlier comment by her coach Craig Cardon claiming that her appearance was far from certain.

"My timing is pretty good at the moment and I'm optimistic about my chances of success in Paris."

The world number eight has suffered a sharp loss of form since last year and pulled out of the Madrid Open earlier this month with the recurring injury, which worsened after her country's Fed Cup win over Spain in April.

The 21-year-old from Belgrade will need a steep improvement in recent form to retain her crown at Roland Garros, which starts on Sunday, after plummeting down the WTA rankings from the number one spot she grabbed after taking last year's title.

She has since won only the Linz Open last October. After another dip in form she was knocked out by unheralded Russian Alisa Kleybanova in the third round of the Australian Open.

Despite the odds stacked against her, Ivanovic is upbeat.

"Obviously I haven't had the preparation I would have liked, but on the positive side I didn't play many matches before the French Open last year too," she said .

If she does badly in the Paris grand slam, Ivanovic will almost certainly drop out of the top 10 - a severe setback after becoming the first Serbian to climb to the WTA summit.

Fellow Serbian Jelena Jankovic, who ended 2008 as the world number one without ever winning a grand slam title, has had to battle her own problems in a disappointing season.

Her lightning reflexes, stamina and speed around the court, qualities that powered her consistent rise in 2008, disappeared after she gained weight during the Christmas break after building up extra muscle and strength.

Jankovic made a fourth-round exit from the Australian Open and her Madrid quarter-final defeat by Swiss Patty Schnyder has made her drop to fifth in the WTA rankings.

"I expected a lot more of myself in Madrid, but it's history and I now have to raise my game for the French Open," Jankovic said after the loss.

"I know where I have to improve and I also have to make radical changes to be number one again."