With the aura of invincibility that surrounds Roger Federer, the most keenly-fought race at next week's Australian Open will be to see who will collide with the Swiss champion in the men's final.

The world number one has probably forgotten what it feels like not to turn up for the title bout at a grand slam. The last time that happened was at the French Open in 2005 when Rafael Nadal tripped him up in the semi-finals.

Since then, the 25-year-old Federer has trampled on one opponent after another to become the first man in the professional era to reach six successive major finals.

He won five of them -- with Nadal again puncturing Federer's title hopes at Roland Garros last June -- and is no mood to take his foot off the accelerator as he targets grand slam title number 10.

"I think it's going to be really tough for people to beat me here. I'm going to make it as hard as possible," said Federer, the winner at Melbourne Park in 2004 and 2006.

Double French Open champion Nadal should have been in pole position to make his date with Federer on January 28.

But a thigh strain coupled with his indifferent form over the past six months could hand the edge, draw permitting, to players such as Andy Roddick or even 2005 Open champion Marat Safin.

Federer, however, warned that Nadal should not be discounted.

"I see him playing very well here," said Federer.

"He's improving on fast courts. For those who still haven't understood yet that he's still a good hardcourt player, or even grass, they should start to wake up. He's really improved a lot."

With a losing 3-6 record against the bullish Spaniard, Federer knows what he is talking about.

During the first six months of 2006 Nadal ran rings round Federer as the Spaniard won all four of their encounters -- in the finals at Dubai, Monte Carlo, Rome and Roland Garros.

GROWING RIVALRY

Three of those meetings were on the Spaniard's favoured clay, giving the world number two a then 6-1 advantage in their head-to-heads and raising a few murmurings over Federer's legitimacy as the world's best player.

Federer knew the grasscourt season would allow him to redress the balance of power.

Yet Nadal's startling run to the second Sunday of Wimbledon signalled that a genuine rivalry was growing.

Federer's dazzling assortment of spin and touch pitted against the thundering groundstrokes and fitness of Nadal left fans agog.

But the Spaniard's Wimbledon heroics appeared to take the fight out of him and put that rivalry on hold as he has since failed to reach another final.

"I don't think I can challenge Roger at the moment," the 20-year-old Spaniard told Reuters recently. "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."

If Nadal's barren run continues, Roddick and Safin will be ready and waiting in the wings, as will local hope Lleyton Hewitt, 2006 runner-up Marcos Baghdatis and Argentine David Nalbandian.

Teenagers Andy Murray, the only player besides Nadal to defeat Federer in 2006, and Novak Djokovic will also be keen to prove their growing stature on the world stage.

Yet it was Safin who was the last man to defeat Federer at the Open. In an epic semi-final in 2005, the Russian came back from match point down to defeat Federer 9-7 in the fifth set and went on to win the title.

The Russian missed his title defence 12 months ago through injury and hence will also want to preserve his unbeaten run over the next two weeks.

Chances are though, that no one will be able to knock Federer off his pedestal.