Roger Federer's tennis wish-list for 2008 will have to be modified after yet another defeat by Rafael Nadal in the Monte Carlo Masters final confirmed there was only one king of clay.

Federer may be the world No1 but he travels to the French Open next month knowing that Nadal has established, once again, the kind of domination on clay that the Swiss superstar enjoys on hard courts and his beloved grass.

Despite starting the year with what he described as "a bout of glandular fever", Federer was confident enough to list his targets for the season as winning an Olympic gold, claiming a sixth Wimbledon title, passing Pete Sampras's record 14 Grand Slam titles and collecting a first French Open title.

Victory in the low-key Estoril clay tournament suggested Federer was becoming a greater threat on the red stuff, building on his French Open final appearance of last year.

However, the 7-5, 7-5 loss against Nadal on Sunday confirmed that, despite his improvement, Federer remains more suspect on clay than any other surface and may suffer the same fate as Sampras, who never won in Paris.

Failing to win the Australian Open, where he complained of a stomach problem not glandular fever, ruined Federer's bid to win all four Slams in the same year. Now he may have to be content with triumphs at Wimbledon and the US Open.

Many believe he may have suddenly become more vulnerable, although Nadal dismisses this notion. He said: "It's impossible to be 100 per cent throughout your career and in the last four years he's done unbelievable things.

"He is the best in the world and is going to continue winning Grand Slam titles. Roger has reached the final at Roland Garros and he is one of the favourites for the French Open."

While the Spaniard is correct about Federer's position in the great tennis scheme of things, when you focus on the clay section of the season, the Swiss player is fallible.

Federer said: "There are only a handful of players who can beat Rafa on clay, he's that dominant. The way he moves the ball and himself around the court is great to see and the matches he wins, he grinds them out. I still feel I can beat him if I play in the right way and that's a feeling I didn't have after Monte Carlo last year."

Federer's only hope appears to be the rumours about Nadal having a foot injury and the belief that the Spaniard cannot go on hitting his forehand with a Zorro-like signature finish without long-term damage to his shoulder.

With neither likely to hamper Nadal this year, Federer needs to be at his peak to have any chance of defeating the Spanish youngster on clay.

The early-season illness which meant Federer had to wait so long to claim a first title in 2008 has clouded the issue. Mario Ancic, the giant Croat, took nearly a year to recover from glandular fever, while Federer played through it.

Federer is quick to dismiss any suggestions he is less than fully fit as the build-up to Paris takes the players to Rome for the next Masters event in a week's time.

"I could have played seven sets if I had to, no problem," he said after the Monte Carlo final. "Hopefully, everything's going to come together in Rome, Hamburg and Paris."

Andy Murray, meanwhile, has another chance to test himself on clay later today when he faces Ancic in the second round of the Barcelona Open.

If the British No1 gets past the Croat, he could face clay-court specialist Nicolas Almagro, with Nadal in the same half of the draw.