That is the view of Indian Wells champion and world No 5 Dominic Thiem.
Nadal is in Monte Carlo for the Masters 1000 event where he is an 11-time champion and he is the favourite to win again this week.
With Roger Federer not involved, Nadal’s biggest challenge is expected to come from Thiem, Novak Djokovic and Alexander Zverev.
Thiem is very strong on the clay with eight of his 12 career titles coming on the surface.
And his three wins over Nadal have all come on clay, with the most recent coming last year in Madrid.
In an interview with the ATP, Thiem was asked how to beat Nadal on clay and he replied: “It is very tough.
“I saw him yesterday practising again and it looked very good again.
“I think it is very important to believe in it.
“I think in here in Monte Carlo and the Roland Garros it is even tougher because these are his conditions.
“It’s so tough to hit a winner against him.
“Rome and Madrid I think is a little bit better for the opponent but I hope I can have some more matches against him this year on clay and try my best again and beat him.”
Thiem begins his Monte Carlo campaign against either Martin Klizan or Federico Delbonis.
And the Austrian says he has big expectations.
“I expect a lot, of course, like in every clay-court season… [There are] only strong tournaments and, especially here, the draw is a joke. It is so strong,” he said.
“In general, the level of men’s tennis is pretty high at the moment. I think everybody has to be ‘full power on’ from the first point of every match, myself as well.
“That is what I will try [to do] and I hope good things are coming in this clay-court season.”