Rafael Nadal believes his record of nine French Open titles can be beaten, even if fellow Roland Garros legend Gustavo Kuerten believes it may take an extra-terrestrial to do it.

“Nine in 10 years. I’m sure it will never happen again. It’s impossible,” said triple champion Kuerten.

“Rafa … he’s not from this world.”

But Nadal, who stayed on course for a 10th title on Saturday when he swept into the fourth round, insists that his record is far from secure.

“First of all, I am from this planet, I think,” smiled Nadal after sweeping into the last 16 with a 6-1 6-3 6-2 rout of Russian Andrey Kuznetsov.

“Second thing, thanks to Guga for the words. Third thing, it’s true that it is probably a tough record to beat. But at the same time, I tell you one thing: if I did it, somebody else can do it.”

Nadal meets Jack Sock next, very much focused on the American giantkiller before even thinking about a potential quarter-final blockbuster with world No.1 and top seed Novak Djokovic.

Nadal is wary of the dangers posed by Sock, who beat 10th seed Grigor Dimitrov in the first round before getting past Spanish claycourter Pablo Carreno Busta.

“He’s a great player,” said Nadal of the youngest American to make the last 16 since the great Pete Sampras in 1993.

“He has an amazing forehand, very good serve, and can play very aggressive and is dangerous. I know I have to be very solid.

“I will try not to let him get into good forehand positions, because I am going to be in big trouble.”