Novak Djokovic has described Rafael Nadal as the 'ultimate challenge on clay'.
The world number one returns to action this week at the Monte Carlo Masters and he will be looking to stop Nadal claim his eighth consecutive title.
The pair went head to head on clay last season with Djokovic getting the better of the Spaniard in Madrid and Rome.
Speaking to the ATP the world number one said: "The fact of the matter is that he probably plays the best tennis in Monte-Carlo, at a clay court tournament aside Paris.
"He has won seven times in a row here. From a personal perspective, I think the conditions are slower than Madrid, which has altitude, Rome, Paris, so maybe that works in his favour more.
"We’ve played already here finals in 2009, good match, but Nadal is the ultimate challenge on clay. He’s the king of clay. He’s the best tennis player ever to play on this surface and one of the best tennis players ever, so that says enough."
It has already been a good season for Djokovic with wins at the Australian Open and Miami Masters and he is looking to claim the Monte Carlo crown for the first time.
He leads an all star field that includes Nadal, Andy Murray, Jo Wilfried Tsonga and David Ferrer.
FemaleFirst Helen Earnshaw