PARIS: An air of uncertainty surrounds the women's event at the French Open starting Sunday, with many of the would-be favourites going into the tournament struggling for form and fitness.

World number two and perennial Grand Slam contender Serena Williams has won the last two majors but hasn't tasted victory on clay in a year and pulled out of her first round match at last week's Madrid Masters with a knee injury.

Serena, who holds the US and Australian Open titles, and her sister Venus, the reigning Wimbledon champion, are bidding to complete a clean sweep of the four Grand Slams, but Serena insists her only goal in Paris is to improve on her third-round exit from last year.

"I'm just glad to be here," she said. "I don't think I am the favourite. It is what it is. Now I feel I want to make all my memories this year."

Reigning champion Ana Ivanovic picked up her first major title at Roland Garros last summer but it precipitated an alarming loss of form that saw her slide from number one to number eight in the world rankings.

"It's true, just after Roland Garros I really lost my way," she said. "But it's in the past now and it’s all a good experience."

Maria Sharapova is another former world number one to have lost ground on her rivals, having been sidelined with a shoulder injury for almost 10 months before returning to action at this week's Warsaw Open.

"I don't have any expectations," she said after losing to Ukraine's Alona Bondarenko in the quarter-finals in Poland.

"I don't think this is the time in my career to have expectations."

The tribulations of the sport's leading lights means the field for this year's tournament looks more open than ever, although current world number one Dinara Safina is in ominous form after winning back-to-back clay tournaments in Rome and Madrid.

Safina will also be under threat from fellow Russian top tenners Elena Dementieva, Vera Zvonareva and Svetlana Kuznetsova, while Ivanovic's Serbian compatriot Jelena Jankovic could also threaten.

But while the Williams sisters can point to a Grand Slam pedigree that has seen them amass 17 singles titles between them, the same cannot be said of the Russians and eastern Europeans.

No-one sums that up better than Safina.

The little sister of Marat Safin knocked Serena off the top spot in April despite never having won a Grand Slam title and admits her priority now is to prove to everyone that she deserves to be where she is.

"It’s going to be another step," said the determined Russian.

"You have steps to take in your life. The first step for me was either to win a Grand Slam or become number one, so I already have one.

"For the next step, I have my whole career and I’m going to continue working hard to win a Grand Slam."

Similarly Dementieva has yet to win a Slam, having lost in the 2004 French and US Open finals, while Svetlana Kuznetsova has struggled to live up to her upset win in the 2006 US Open.

The two Serbs are even more perplexing.

Ivanovic was a popular and convincing winner in Paris last year, defeating Safina in a one-sided final, but with the tennis world at her feet, she then went into a slump from which she is still struggling to emerge.

A knee injury that kept her out of the Madrid Masters has done little to raise the hopes of her fans, but the ever-sunny Belgrade beauty is hopeful that Paris will once again bring out the best in her.

"As soon as I set foot on Phillipe Chatrier court, all the emotions come flooding back every time," she said.

"It really gives me an extraordinary feeling. I can't wait to get back to Paris."

Jankovic, like Safina, reached the world number one spot last year despite failing to win a Grand Slam event, but her form has been poor recently as injuries have taken their toll.