Federer, who won his sole French Open title in 2009, is refining his own clay court game in this week???s Istanbul Open, the first ATP Tour event to be held in Turkey and the first time that the Swiss star has visited the country.
Nadal, who with the exception of Federer’s win has taken every French Open since 2005 to make nine in total, has struggled in recent weeks and failed to get past the third round at last week’s Barcelona Open.
But Federer still thinks Nadal in the man to beat on the red clay of Roland Garros, along with in-form world No 1 Novak Djokovic.
“At the French Open, Rafa for me is still the favourite alongside Djokovic who has been playing so well,??? said Federer.
“Even though his (Nadal’s) form is not as good as in previous years, I still believe when the French Open rolls around he is going to be very difficult to beat.”
Federer, 33, is himself looking to find his form on the clay, having lost in the third round to Gael Monfils at the Monte Carlo Masters this month.
“It’s about getting used to the sliding, deciding how aggressive I want to play,” said the world No 2.
“I have been on hard courts for seven-eight months so it needs some adjustments.
“My game is going to get better and better as we move along.”
Federer, who celebrated his arrival in Istanbul by thumping a ball into the Bosphorus that divides Europe and Asia, is the star attraction in the tournament along with the Bulgarian world No 11 Grigor Dimitrov.