The virus forced the 26-year-old to withdraw from his traditional build-up to the Open at the invitational Kooyong Classic and with him also skipping the Doha tournament last week, he will enter Melbourne Park with no match practice.

The last person to enter the season's opening Gand Slam 'cold' and win the title was Andre Agassi in 1995, though one of Federer's closest rivals doubts the lack of matches would effect the Swiss too much.
"I can safely say that none of us are worried about Roger's preparations for the Open," world number six Andy Roddick told reporters ahead of the fortnight tournament beginning from Monday.

Federer, arguably the greatest player to have picked up a tennis racket, is seeking his fourth Australian Open trophy and 13th Gand Slam title. He has not been beaten at Melbourne Park since losing to eventual champion Marat Safin in the 2005 semi-finals and the big Russian, who is now healthy after two years of injury, looms as one of his biggest threats.

The twice Gand Slam winner, considered by his peers to be one of the few players able to challenge Federer when in form, has been plagued with knee injuries in the past two years but said he feels healthier than he had in "many years".

World number two Rafael Nadal will again be one of Federer's main rivals for the title at Melbourne Park but the enigmatic David Nalbandian's chances could have ended with a back injury he sustained while practising with Safin earlier this week.

The Argentine, who celebrated his 26th birthday last week, beat Federer and Nadal twice each late last year and has the all-court game to challenge both. However, back spasms on Wednesday forced him off the court against Safin and doctors advised him to rest for at least four days, cutting short his preparations.

Novak Djokovic, who beat Federer in the final of the Montreal Masters before losing to the world number one in the US Open final, will be looking to cement his top-three status.

Local favourite Lleyton Hewitt, who has long campaigned for Australian Open organisers to speed up the courts, could struggle on the new Plexicushion courts with several players indicating they think they are slower than the old Rebound Ace surface.

Hewitt's preparations also suffered with a loss to compatriot Chris Guccione at the Sydney International tournament.

He has also not beaten Federer since a Davis Cup match in 2003.