Nadal has an excellent record against the Swiss maestro, defeating him six times in nine matches, but Federer won the last two meetings in last year's Wimbledon final and Masters Cup semis in the course of his magnificent 2006 season.

Switzerland's tennis player Roger Federer walks past a poster of Spain's tennis player Rafael Nadal as he arrives for a news conference in Madrid October 15, 2006. [Reuters]

"I don't think I can challenge Roger at the moment," the 20-year-old Spaniard told Reuters. "Roger is the best by far. He is at another level.

"Just look at the numbers, Roger's are so impressive and it's just unbelievable."

Nadal said he was trying not to think too much about the world number one and defending Australian Open champion, focusing instead on his own performances.

"I am only trying to improve my game, and specifically those parts of my game that will help me play better on surfaces other than clay," he said.

Nadal missed last year's Australian Open due to injury but enjoyed his two previous appearances in the tournament, reaching the third and fourth rounds before losing to local favourite Lleyton Hewitt, including a five-set thriller two years ago.

"I have a big motivation because when I come back to Australia it's one of my favourite tournaments and the weather is perfect for me and it's a very nice place," he said.

"Melbourne is one of my favourite cities in the world.

"Every time I come to Australia to play I play a very good game. It's important to come back with confidence."

Nadal, twice French Open champion, lost in the semi-finals in Chennai last week but was not too despondent heading into this week's Sydney International.

"It was a good tournament for me and I'll take it forward to Sydney," he said.

"Every time I enter an event I want to win but so does the rest of the draw. My goal is to keep improving on all surfaces since I am still very young and if the titles come that would be great."