Defending champion Nadal was stretched to the limit by the 6ft 10in American and called on all of his fighting qualities to come back from behind and win 6-4 6-7 (2-7) 6-7 (2-7) 6-2 6-4.

The tall American's powerful serve forced Nadal to stand further back when receiving serve than he usually would and the world number one had to adapt to try and break the Isner serve. When Nadal managed to force break points a booming unreturnable Isner serve often snuffed the chance out.

The American played extremely well in the tie-breaks and buoyed by the support of the Philippe Chatrier crowd went ahead by two sets to one.

The new, faster balls that are in use here at Roland Garros will have suited Isner's game more than Nadal's but the Spaniard is known for his fighting and battling qualities and he called on all resources to battle back into contention and take the fourth set and force a decider.

Isner visibly wilted towards the end of the final set and Nadal continued his onslaught to grind the American down and after 4 hours Nadal had match point and sealed his place in the second round with a pulsating unreturnable forehand to Isner's backhand corner.

"It was like a penalty shoot-out," said Nadal after the match. "Isner's serve is almost unstoppable at the moment. In the tie-break you play under pressure all the time.

"It's always a very, very close match against John because you play under pressure all the time and at moments in the tie-breaks I didn't play very well, I was too nervous."

Nadal now goes on to face fellow Spaniard Pablo Andujar in the second round.