Oddsmakers have established world No. 1 Novak Djokovic as the French Open favorite, but Roger Federer says nine-time Roland Garros champion Rafael Nadal and Djokovic are the co-French Open favorites in his mind.

"At the French Open, Rafa for me is still the favorite alongside Djokovic who has been playing so well," Federer told the media in Istanbul. "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."

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The second-ranked Swiss has a first-round bye at the inaugural TEB BNP Paribas Istanbul Open. Federer will face either Marsel Ilhan or Jarkko Nieminen in his opener. 

After losing to Gael Monfils in Monte Carlo earlier this month, Federer said he's aiming to make more adjustments to his clay-court game this week in Istanbul.

"It's about getting used to the sliding, deciding how aggressive I want to play," Federer told the media. "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."

Photo credit: TEB BNP Paribas Istanbul Open