Former No. 1 Carlos Moya says that Rafael Nadal is not unbeatable on clay and adds that there are no more surface specialists at the top of the game.

"No one is unbeatable on any surface,” Moya told Marca. "If you ask the players who'll get more points on clay this year, obviously they will say it will be Rafa. But on a bad day, bad night, a bad match, anyone can have one...The specialists we saw a decade ago no longer exist. Before there were players like Pete Sampras, Andre Agassi and Goran Ivanisevic who specialized on super fast courts or grass and players such as Guga Kuerten who had to do so much just to get good on hard courts...Now you have players who do well on fast surfaces and on clay and vice versa. Those who can dominate on any surface are the ones at the top: Nadal, [Roger] Federer or [Novak] Djokovic and before it did not happen."

Moya, who retired last year after a series on injuries and now is a player liaison for the tournament in Madrid, added that Roger Federer is feeling his age, but still has a shot at another Grand Slam title.

"You can’t do anything against genetics and the body, as you get older the body loses power," said Moya, who also believes that Djokovic will eventually reach No. 1. "Federer's case reminds me of [Pete] Sampras, when everyone thought he should retire and in his last tournament, he won the U.S. Open. The greatest player in history can never be counted out. I hope Federer keeps playing his best because it is a pleasure to watch him play. I hope he can extend his career to its fullest and don’t rule out him winning another Grand Slam. Wimbledon is the one where he’ll have the most chances. When he retires, we will realize how big it is and we will miss him."—Matthew Cronin