Guillermo Vilas says he is not impressed by Rafael Nadal's [ Images ] winning streak on clay even though the Spaniard will break the Argentine's record if he comes through his first round at the French Open [ Images ] on Monday.

The 19-year-old Nadal has been undefeated on the slow surface in his last 53 matches and looks set to add a 54th consecutive win when he kicks off his title defence at Roland Garros [ Images ] against Swede Robin Soderling [ Images ].

"First of all, Nadal's performance is spanning over two years, which is not the same," Vilas, who set the record in 1977, told Reuters on Monday.

"Then, I have the feeling he added easy tournaments on his schedule just for that purpose," the 53-year-old added.

Vilas, who confessed he had to call the ATP to have confirmation of a record he had ignored, had his 1977 run ended in the Aix-en-Provence tournament semi-finals by Ilie Nastase.

"I did not lose to a player but against a racket," he said, referring to the double-strung racket the Romanian was using at the time.

"I could not play him. When I was 6-1 7-5 down, I threw in the sponge," said Vilas, who had won the Tehran, Bogota, Santiago and Buenos Aires tournaments that year.