You can confidently assume that when Roger Federer describes Marat Safin as his toughest opponent, the world No.1 is applying a bit of Swiss diplomacy.

Federer, who meets Safin in the Australian Open semi-finals, has beaten the Russian in six of their seven career meetings, including last year's Melbourne Park decider in straight sets.

Safin's only victory over Federer came in his home city of Moscow three years ago and, even when things get tight, the Swiss maestro can count on squeezing through a tiebreak.

Federer has won all five tiebreakers against Safin, including the most recent - a 20-18 nailbiter in last year's Masters Cup semi-final in Houston.

While admitting that his remarkable 24-0 record over top-10 rivals over the past 16 months made it difficult to nominate his toughest opponent right now, Federer eventually plumped for the big Russian.

"I've beaten all the top-10 players so regularly, so it makes it hard to obviously pick one. I have the feeling Safin is playing really good," said the top seed and odds-on favourite for the title.

"The other top-10 guys, you always know on a given day they can upset you any time, so I'm really looking forward to the contest with Safin.

"I have the feeling he's playing good again and he had a great finish last year, good start again. So it's going to be a really hard match."

No doubt, though, much harder for Safin, who at least took heart from his near miss against Federer in Houston.

"I learned a little bit more," Safin said of the 6-3 7-6 (20-18) loss two months ago.

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