MELBOURNE (AFP) - Andy Roddick backed world number one Roger Federer to mount a strong defence of his Australian Open crown despite pulling out of this week's Kooyong Classic with a stomach virus.

The American, who beat Federer in the final of the eight-man event last year, said the Swiss would recover for the year's opening Grand Slam, which starts on January 14.

"None of us are worried about his preparation for the Open," Roddick joked, drawing laughs at his press conference. "I'll sleep OK tonight."

He added: "It's impossible for me to say how he might go, I don't know how he feels.

"But Kooyong seems to be good preparation for Roger. This (illness) won't help, but if anyone can play his way into form, that would be Roger."

Word from the Federer camp suggested the 12-time Grand Slam winner was resting under doctor's orders as valuable training time for the Open slips away.

Roddick meanwhile begins his campaign at the Kooyong event when he faces Croatian Ivan Ljubicic on Wednesday.

Federer's substitute Nikolay Davydenko will take on Marcos Baghdatis, Fernando Gonzalez will play Argentine David Nalbandian and Britain's Andy Murray will play former Australian Open champion Marat Safin.

Safin, who cut last season short in October due to disappointing form, said he was ready to attack this year.

But first, he has to acclimatise to the new blue Plexicushion court, which has replaced the former Rebound Ace surface.

"I've been working for six weeks in Spain -- I got here early to get used to the colour," he joked. "We just have to deal with it.

"I think it could be a good year for me, my knee doesn't hurt and hopefully I can stay this way for the whole season."