Rafael Nadal can raise the roof and end great debate

For someone who supposedly hated tennis, and hated it "with a dark and secret passion", Andre Agassi has a remarkable collection of trophies.

Perhaps The Man Who Hated Tennis loathed the sport the most when he won each of the four grand slams and a gold medal at the Olympics, or perhaps it was when he ripped through the field at the season-ending championships, or when he and his American buddies scored the Davis Cup.

For now, he is the only player to have won everything of note in the men's game. Over the next eight days in Greenwich, Rafael Nadal will be trying to emulate Agassi, as an end-of-year title would give him the full set.

In so many ways, Nadal is everything that Agassi wasn't: the Majorcan loves his tennis, he doesn't tend to look at ease in the arc-lights (though he did open up during a television interview in a South Bank hotel the other day to say he was scared of the dark, just a few minutes after Roger Federer had admitted to a fear of roller-coasters), and he has his own hair.

And Nadal was unimpressed with Agassi's disclosure in his autobiography that he took crystal meth, a highly addictive stimulant, and then lied in a letter to the men's tour to avoid a ban after failing a dope test.

For all that, if Nadal were to achieve what only Agassi has achieved before, by winning the ATP World Tour Finals at the O2 Arena, that would only provoke further debate that he is possibly the greatest player of all time. Nadal, whose last appearance on court in London ended with a celebratory forward-roll on the Wimbledon grass, has the opportunity to give himself a more 'complete' career than Federer.

It was after the world No 1 joined the career grand slam club, winning this year's US Open to become the seventh man in history and the youngest of the modern era to win all four majors, that many started to seriously consider whether he, not Federer, was the finest of all time.

Though Federer has done the career slam, and has won season-ending tournaments, his Olympic gold at the Beijing Games was from the doubles competition as Nadal was the singles champion, and he has never come close to lifting the Davis Cup with Switzerland. John McEnroe used to be unequivocal about Federer, yet last week he referred to the Swiss as only "one of the greatest players".

This has been a superb season for the trophy-chewing Nadal, as he munched on three grand slam cups, with victories at Roland Garros, Wimbledon and Flushing Meadows, so if he were to win in south-east London that would have the Roger-or-Rafa swingometer moving his way. "There's an argument that Nadal could eventually be considered the greatest player," said McEnroe.

Would Rafa have more chance of success if they sliced the top off the O2 Arena? Inside, the received wisdom on Nadal is that he struggles with a roof over his head, and there is no getting away from the fact that, of his 43 career singles titles, 42 have come at outdoor tournaments. You have to spool back five years, to the hard-court championships in Madrid in 2005, for the last and only time that Nadal won an indoor tournament.

By way of comparison, Andy Murray has won half of his 16 singles titles inside, which has everything to do with the different climates by the Mediterranean and in Scotland. It sounds as though the court this week is low-bouncing, which is not good news for Nadal, as he can have difficulties when "there is no life in the ball".

For Nadal, winning this tournament could be trickier than winning Wimbledon. Still, many were saying before this year's US Open that his game would adapt poorly to the cement of New York City, and look what happened there.

If Nadal can win on the fast concrete in America, he can win on a medium-paced court in Greenwich, low bounces or not.

"Maybe Rafa hasn't played his best indoors in the past, but he's capable of playing well anywhere," said Murray, who opens the tournament against Sweden's Robin Soderling this afternoon.

What matters most of all is how Nadal is physically. Last season, with his cranky knees, he failed to win a set in all three of his round-robin matches against Soderling, Nikolay Davydenko and Novak Djokovic.

There is a degree of concern this season about what state his game will be in, since he missed the last regular tournament of the calendar, the Paris Masters, after over-training and giving himself tendinitis in his shoulder.

His match against Andy Roddick will be his first for more than a month. Still, it would seem that he only missed the tournament as a precaution, as he reported here that his shoulder was "perfect".

No one is fretting about how Nadal's body will hold up, and on the cover of the December issue of GQ magazine, just above an image of the actor Robert Downey Junior, there is an invitation to turn inside for 'fitness training tips from Nadal'. That is not a feature you would have found yourself reading this time a year ago.

ATP World Tour Finals

The season-ending tournament is restricted to the best eight players in the world. The players are split into two groups with the top two from each group qualifying for the semi-finals on Saturday, with the final next Sunday.

Group A

Rafael Nadal
Novak Djokovic
Tomas Berdych
Andy Roddick
Group B

Roger Federer
Robin Soderling
Andy Murray
David Ferrer
Sunday: Murray v Soderling; Federer v Ferrer
Monday: Djokovic v Berdych; Nadal v Roddick