Only an early shock can prevent the runaway world number one from adding to his Grand Slam haul, according to former champion Jim Courier.

The American, himself a former world number one and twice champion of the Melbourne grand slam, faced Pete Sampras in his prime in the 1990s and knows only too well what today's challengers are up against when they face runaway rankings leader Federer.

"I think everyone has to be wondering 'How do you beat Federer?'," he said on Tuesday.

"He's not only beating guys, he's crushing them, and I'm talking about guys in the top 10. He's not even being pushed by a guy like Lleyton Hewitt [Images], who was playing the second best tennis in the world at the end of last year.

"I would like my chances playing against Federer more in the first couple of rounds than I would from the quarter-finals on.

"You might be able to sneak in and get him early on but if you catch him in the semi-finals, I think you're pretty much done."

MAGIC POTION

Courier, who these days plays on the Delta Tour of Champions seniors circuit, said he was not at all surprised that 34-year-old Andre Agassi [Images] was still going strong.

"If he finishes another season in the top 10, why wouldn't he continue?" he said.

"No-one's asking the guy ranked number nine when he's going to retire and Andre is ranked number eight.

"He has obviously found that magic potion that keeps him inspired after 20 years on the tour and it's a marvel.

"He is still a force. The match he played against Safin in the semi-finals of the Australian Open last year proved that.

"In conversations I have had with him, he was working very hard in Las Vegas [Images] to get himself ready for the season and he was incredibly enthusiastic."

The Australian Open runs from January 17-30.

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