But the questions are piling up.

The 26-year-old's loss in Hamburg took him to a 1-8 record against Nadal on clay while, in both the Monte Carlo and Hamburg finals, he surrendered healthy leads.

If that wasn't worrying enough, there is the growing threat posed to both men by Novak Djokovic, the world No 3 and the best player in the world in 2008.

The Serbian, who took Federer's Australian Open title and showed his ability on clay with the Rome trophy, only turned 21 on Thursday.

"Federer has just two or three years to realize his dream," said Sampras, when asked if the Swiss will ever win Roland Garros.

"He has the game to do it but things need to fall into place for him.

"Once he hits 29 or 30 the Djokovics and Nadals will be in their prime and it'll become a little tougher," added Sampras, whose best showing at Roland Garros in 13 attempts was the semifinals in 1996.

Federer, who has six clay-court titles in his 54-trophy collection, is nothing if not positive.

"I'm pushing Rafa and I have the feeling I can beat him if I play the right way," he said.

"I feel like my defensive skills are getting better and better. To compare to other years, I always feel like I'm bringing more game into my claycourt game over the years, even though it was good before. I just think I'm a more clever clay-court player today."

Twelve months ago, Federer had Tony Roche in his corner as coach; twelve months on, he has turned to Jose Higueras, the grizzled Spanish clay-court specialist who guided Jim Courier and Michael Chang to victory here.

Both Americans believe it's a smart decision.

"Jose understands the mind of a champion, knows how to deliver information tactfully and knows how to prepare a player as well as anyone you'll find," said Courier, the winner in 1991 and 1992.

Chang, who was just 17 years and three months old when he was champion in 1989, also thinks Higueras can be a key figure.

"Jose's knowledge of the surface and Spanish tennis can bring a new understanding of clay-court tennis to Roger's game," Chang said.

(Agencies via China Daily May 23, 2008)