He made it to the second round in New York before losing in straight sets to number 22 seed Younes El Aynaoui, of Morocco. With a shaggy hairstyle and street-style clothes, the Spanish left-hander was an unlikely tennis superstar in the making, but even then his muscular, power-packed style gave a hint of great things to come.

As the word spread across the ATP circuit like Chinese whispers, Nadal won two Challenger titles to finish the year in the top 50, the second youngest in history to be ranked so high.

But a series of injuries - including a stress fracture of his left ankle - meant that it wasn't until 2005 that Nadal played the French Open for the first time and his career really took off. Since then, he's never been beaten on the red clay of Roland Garros, claiming four titles and 28 consecutive victories.

And, with the Australian Open and Wimbledon crowns now in his trophy cabinet, Nadal has six grand slams, including three of the last four - plus the Beijing Olympic gold medal, which he won last August soon after claiming the world number one ranking. He's the first man since Andre Agassi to grab major titles on three different surfaces.

Nadal's dominance of his biggest rival, Roger Federer, has become so lopsided - he's won 13 of 19 career meetings against the once invincible Swiss - that injury rather than any opponent is seen as the main obstacle to the 22-year-old setting the all-time record for grand slam singles' victories.

Pete Sampras has 14 majors while Federer is stuck on 13 after the Australian Open: his third grand slam final defeat in a row to his nemesis.

'Unless Nadal gets a bad injury, I am backing him to beat the record,' said Mark Kratzmann, the Hong Kong-based coach and former Australian Davis Cup player. 'He will win the French three to four more times and could pick up as many as eight in the other three grand slams over time.'

With success at Melbourne Park and the All England Club, Nadal has completed the difficult transition that other clay-court champions like Gustavo Kuerten, Sergi Bruguera and Thomas Muster were never able to make.

A combination of being a left-hander and hitting with so much topspin means Nadal is a potent opponent when facing right-handers like Federer. Indeed, it was fellow lefty Fernando Verdasco who gave Nadal his toughest match at the Aussie Open in an epic five-hour semi-final.

'One of the most difficult aspects of playing against Nadal is that his balls are fast, high and create great angles,' says Dr Choi Hee-june, tennis director at Mission Hills Golf Club in Shenzhen. 'Keeping up with Nadal for just one set is demanding enough, but after that it is almost impossible.

Kratzmann added: 'The constant pressure his heavy crosscourt forehand builds on the right-hander's backhand means that opponents need to take an extra two to three steps per shot which adds up to extra kilometres during a five-set match.'

What makes Nadal even harder to beat is his athleticism from the baseline with a foot speed to almost match the velocity of his ferocious ground-strokes. However, in a relatively short career, he's had so many leg injuries - including knee tendinitis that cut short his 2008 season - that some experts predict a decline in his physical prowess will bring a premature end to his dominance.

But not Kratzmann nor Choi. They say that instead of following the pattern of former grand slam champions like Lleyton Hewitt and Michael Chang, who peaked in their early 20s then faded, Nadal's career will go the distance. Kratzmann compared him to four-time grand slam champion Guillermo Vilas, the powerful Argentine of the 1970s and 80s who won three tournaments after his 30th birthday.

'Chang and Hewitt are counter-punchers but Nadal has massive weapons from both sides so although it looks like he's working hard, I don't think it's going to bother him in the long-term,' Kratzmann says. Choi adds: 'Although his style is physically demanding, I expect him to have a long career.'

Nadal's next big target will be May's French Open in Paris where he will be an almost unbackable favourite to win for a fifth consecutive time, surpassing Bjorn Borg's men's record of four straight titles.

Unlike the gracious Federer who patiently does almost endless interviews in English, French and Swiss-German, Nadal clearly enjoys the process a lot less and prefers to keep his answers on a more practical level, rolling his eyes at repeated questions about his place in tennis history. Even so, there's something likeable about the young man from Majorca.

During one of our interviews, Nadal wore his own personalised 'Marquer Histoire' (To Mark History) polo shirt in which the years of his French Open victories were written in a single column and crossed off in almost routine fashion.

It's a pretty good bet that the year 2009 will also have a line through it soon on what is becoming a rather crowded breast pocket for Spain's irresistible force.

Sky's the limit

Nadal has overcome a series of injuries early in his career, to become the first man since Andre Agassi to grab major titles on three different surfaces

Of all his impressive achievements, it's his four French Open wins at Roland Garros that stand out. Since 2005, the Spaniard has had this many consecutive victories in the Paris showpiece: 28