Novak Djokovic
Rafael Nadal is the ultimate challenge when it comes to playing on clay says Novak Djokovic Getty

Novak Djokovic believes Rafael Nadal is the ultimate challenge when it comes to playing on clay and admits that he is the player to beat. The Serb was praising his long-time rival in reference to his decade long dominance in Monte Carlo, where the Spaniard is targeting a 10th title this year.

Nadal has won 59 of the 63 matches he has played since his first tournament at the Principality and looks on course to take the title against this year. The 14-time Grand Slam champion progressed to the semi-finals on Friday after beating Argentine Diego Schwartzman in straight sets and will next meet David Goffin, who knocked out world number two Novak Djokovic.

The Spaniard's coach and uncle Toni Nadal had labeled the Serbian star as Nadal's main rival when it comes to winning clay court tournaments ahead of the Monte Carlo Masters, but the two will not face each other this time around. Djokovic will return for the Madrid Masters next month where he is the defending champion.

"Winning nine titles in any tournament around the World is an incredible achievement especially in one of the best tournaments in the World. He is not called King of Clay for nothing. He is the ultimate challenge on this surface and the player to beat," Djokovic said, as quoted by Tennis World USA.

World number one Andy Murray also joined Djokovic in praising the 14-time men's singles Grand Slam champion and believes Nadal being left-handed helps on clay as he can generate more spin and utilise the angles better on court.

The Scot is also struggling for form and was knocked out of the Monte Carlo Masters in the round of 16 by Spaniard Albert Ramos-Vinolas. Murray, who is coming back from an elbow injury, has confirmed that he will play the next tournament in Barcelona.

"I think to win it for ten times would be incredibile. It's amazing what he has done here. Also being left-handed helps because he can use the angles on the court so well with the spin he generates. It's always difficult to dictate points against him," Murray said.