Former world number one Roger Federer is not ready to concede the French Open will be a straight fight between Novak Djokovic and Rafael Nadal.
Djokovic has put together a run of 32 consecutive wins this year, while Nadal is a five-time winner of the Roland Garros tournament.
Federer, Djokovic and Nadal are sharpening up their preparations for the French Open at the Rome Masters.
And Federer said: "The other players are right behind waiting to strike."
Many in the tennis world feel the once dominant Federer, a winner of 16 Grand Slam titles, is a fading force, particularly on clay. But the 29-year-old from Switzerland does not see it that way.
He said: "It's definitely an interesting time right now that Novak hasn't lost all season long. It makes it a new, different situation, but for me it doesn't change a whole lot.
"Right now [Djokovic and Nadal] are playing better than me and better than other players. I feel like everybody can play on all the surfaces these days and that makes it extremely hard to win all these big tournaments."
Federer was buoyed by taking a set off Nadal in the semi-finals of the Madrid Masters, and said: "I again was really close up against Rafa and so all I need to do is to get that step further and I hope I will do that this week."
Federer's first opponent in Rome on Wednesday will be former Australian Open runner-up Jo-Wilfried Tsonga. Nadal opens against either Italian qualifier Paolo Lorenzi or Brazil's Thomaz Bellucci, who reached the Madrid semi-finals before losing to Djokovic.
Djokovic starts off against Polish qualifier Lukasz Kubot.
“The results of my tests showed a tear in the hip... I have already started rehabilitation and I will do all I can to be in Paris”
Juan Martin del Potro is a doubt for the French Open
Juan Martin del Potro
is a doubt for the French Open, starting on 22 May, after revealing he has a torn hip muscle.
The former US Open winner pulled out of last week's Madrid Masters and has undergone tests on his injury.
"The results of my tests showed a tear in the hip," the Argentine wrote on his Twitter page.
"I have already started rehabilitation and I will do all I can to be in Paris."
Del Potro, who reached the semi-finals at Roland Garros two years ago, has been beset by injury in recent times and missed most of last year with a wrist complaint.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.