Defending champion Spain's Rafael Nadal, behind, looks at top-seeded Roger Federer of Switzerland as they cross each other for training sessions yesterday at the Roland Garros stadium in Paris, on the eve of the French Open. - AP

PARIS (AP):

EVERYTHING ABOUT tennis is topsy-turvy heading into the French Open.

Roger Federer, seemingly invincible against anyone but Rafael Nadal, is off to his worst start to a season since 2001. Nadal, meanwhile, recently lost a match on clay - for only the second time in three years.

Justine Henin, like Nadal the three-time reigning champion in Paris, suddenly retired this month at the age of 25, the first woman to walk away from the sport while ranked number one.

There's more: New number one Maria Sharapova and Serena Williams also pulled out of recent matches because of injuries; high-profile players are openly complaining about tour calendars and commitments and Andy Roddick, the highest-ranked American man, is sidelined by a bum shoulder. It's enough to make one wonder which way is up as the tennis world gathers at Roland Garros for the season's second Grand Slam tournament, which begins today.

13 trophies

Start with Federer, whose 12 major singles championships put him two shy of Pete Sampras' career record. Consider this: Each of the past six years, Federer arrived at the French Open with at least two - and as many as six - tournament titles to his credit. The past three seasons, he was a combined 103-9 with 13 trophies entering the French Open.

And in 2008? He is 26-7 with only one title. He was upset by eventual champion Novak Djokovic in the Australian Open semi-finals in January, ending Federer's streak of reaching 10 consecutive Slam finals.

Federer gives off nothing but optimism, however.

"I'm feeling where I want to be shortly before a really important stretch of tournaments," he said on Friday. "And it starts here in Paris, so I feel good about my chances again."

Nadal will attempt to become only the second man in history to win the French Open four years in a row, joining Bjorn Borg.

"He's very superior on this surface," said Djokovic, who could meet Nadal in the semi-finals. "His main advantage here is his physical strength and his power and ability to get all the balls back."

done for good

Henin, also, could have been trying to win a fourth French Open in a row. But she says she's done for good, an out-of-nowhere announce-ment that leaves Williams as the only past Roland Garros champion in the women's field.

"Am I surprised? Maybe a little bit," Sharapova said about Henin's decision. "But ... if I were 25 and I've achieved the things that she's achieved in her career, I feel like there's a lot more to life to explore."

Henin's absence gives more hope to someone such as Sharapova, trying to complete a career Grand Slam, or Ana Ivanovic and Jelena Jankovic, attempting to claim a first major championship.

Nadal was hampered by foot blisters during his loss to Juan Carlos Ferrero at the Rome Masters two weeks ago, one of two defeats in his last 110 matches on clay.

That tournament had a record five withdrawals, and both semi-finals ended with players quitting for health reasons, the first time that happened at any Masters Series event. One of the players who stopped was Roddick, and he later pulled out of the French Open, where he's won a total of two matches since 2002.