Soon to be world number one Rafael Nadal said Tuesday he was still feeling weary after his first training session here in Beijing ahead of the Olympic Games competition.

Just hours after flying in to the Chinese capital, Nadal joined Spanish team-mate Tommy Robredo on court seven — current world number one Roger Federer was practising on centre court — for a light work out.

After what amounted to little more than an extended warm-up, with both players running through their ground strokes, volleys, smashes and serves, followed by a game of headers and volleys at the net, Nadal spoke of his tiredness.

"It's too soon to say anything about my condition, I only arrived on Monday and I've got jet-lag but I'm more tired than normal," said the 22-year-old.

Nadal is enjoying his best season yet and will take over from Federer at the top of the ATP rankings on August 18.

He has spent 159 consecutive weeks in Federer's immediate shadow, with the Swiss master spending a record 236 weeks atop the world.

But Nadal beat the Fed-Express in both the Roland Garros and Wimbledon finals this year and has even started the North American hard court season in fine fettle, winning in Toronto and reaching the semi-finals in Cincinnati last week.

What's more, the clay-specialist Nadal, who previously has been unable to reproduce equal results in the second half of the season as in the first, has proved already that his form isn't dipping.

However, he is aware that he can't always be expected to keep up his clay-season success into August and beyond.

"The second half of the season is tougher than the first especially if you've played a lot of tough matches on clay like me," he said.

"It's tough to stay at 100 percent throughout the whole season.

After all these matches I'm more tired than the rest." Nadal is widely considered to be the strongest and even fittest player on the circuit and he will have to be if he is to succeed at the Olympic tournament, which starts on Sunday.

He has the best record of anyone on tour this year, winning seven titles and with a 64-8 win-loss record.

That compares favourably even to Federer who has just two crowns and a 44-11 record.

But what that also means is that Nadal has played 17 matches more than Federer this season — 72 compared with 55.

Ironically the next three players in the rankings — Serbian Novak Djokovic, Russia's Nikolay Davydenko and David Ferrer of Spain, have all also played just 55 matches.

It means that no-one is coming into this tournament with as much having been taken out of the tank as has Nadal.

And with the heat, humidity and pollution likely to have some sort of an effect on players' physical condition throughout the tournament, the Olympics may prove one too far even for Nadal.