Melbourne, Jan 13 (Agencies): Spanish tennis star Rafael Nadal has already achieved a career Grand Slam but has never owned all four major titles at the same time.

That may all change for the Spaniard in next week's Australian Open when he vies with his great rival Roger Federer for the first major of the season. Nadal became only the seventh man in history -- and the youngest at 24 in the Open era -- to claim a career Grand Slam of the four major tournaments when he conquered Novak Djokovic in the US Open final last September.

Nadal finished 2010 reigning supreme at the top of the rankings and enters the Australian Open 3,145 rankings points ahead of Federer, aided by his French Open, Wimbledon and US Open wins.

And Nadal admits he may never have a better chance than in the coming fortnight of taking possession of all four major crowns simultaneously, a feat not accomplished since Rod Laver in 1969.

"In fact," Nadal said, perhaps sensing that an improving Federer could take away one of his other Grand Slam titles this year, "it's going to be the one chance I have in my life."

An Australian title is among Nadal's nine Grand Slams after he downed Federer in a classic five-set final in 2009.

But Nadal comes into the new season recovering from a fever that left him lethargic in a straight-sets semi-final loss to Russian Nikolay Davydenko at the Qatar Open.

He delayed his long flight to Australia to rest and began practising in Melbourne early this week to shake off the cobwebs for his opening encounter at the Open.

Nadal said he had not stopped competing or practising since he left his home in Mallorca to fly to Abu Dhabi for an exhibition tournament on December 30 ahead of the Qatar Open.

Inevitably the debate over which player is the greater will reignite in Melbourne as Nadal and Federer aim for a place in the January 30 final.

Despite Federer's record 16 Slams, Nadal holds a decisive 14-8 record over their 22 meetings on the tour.

Nadal, who has been ranked one or two since 2005, modestly plays down the constant comparisons between the two.

"I think the talk about if I am better or worse than Roger is stupid, because the titles say he's much better than me," Nadal said recently.

"So that's true at that moment. I think that will be true all my life."

But Nadal's progress, at five years younger than Federer, suggests he will surpass the Swiss master by career's end.

"I'm going to work to be ready and be competitive to try to be in the top positions to compete to keep winning titles," Nadal said.

"But the pressure for me is going to be the same. I try to play well, try to compete against everybody, and try to be in the final rounds."

Nadal will be under pressure to defend his three Grand Slam titles and their rankings points this year, but he had an early exit here last year when he retired from his quarter-final against Andy Murray with knee trouble.

The Spaniard is an immensely popular figure and recently reached a milestone by registering more than 5,000,000 fans on his official Facebook page.