Andy Murray believes the failure of Pete Sampras and Roger Federer to win the French Open proves the clay court Grand Slam is the toughest on the men's tour.

Murray has won two clay-court matches at the Monte Carlo Masters this week to show he could be a contender in Paris but tomorrow he comes up against world No3 Novak Djokovic in the last 16.

Djokovic, a close friend and rival from their junior days, won the Australian Open in January to put clear water between himself and the British No1. Murray is set to rise up the ranking ladder from his present 20th place but he needs to beat players such as Djokovic to confirm his own top 10 claims.

Murray, who yesterday claimed a straight-sets win over Filippo Volandri, of Italy, said: "I look forward to the challenge of playing on clay at the French Open purely because I believe it's the hardest Grand Slam to win.

"You look at the two best players in history - Federer and Sampras. Sampras didn't manage to win it and Federer hasn't managed to yet. So it proves it's the hardest.

"I think I can play well on clay but it's understanding the right way to play because I have a lot of different variations in my game.

"I can sometimes play attacking, sometimes play defence. It's just making sure I do the right things at the right time.

"I am not surprised at the tournaments Novak's won. The consistency of his results has been unbelievable.

"He's made the semis of every Grand Slam and played well in a lot of Masters Series events."