MELBOURNE, Jan 19 - Marat Safin will be gearing up for yet another bruising encounter at the Australian Open on Friday when he faces Andy Roddick in a third-round showdown.

The temperamental Russian has already been on court for more than seven hours after being dragged through two successive five-set marathons.

On Friday, he will have to be on high alert as he faces the thunderbolt deliveries of Roddick, who said on Wednesday the pair were too good to be meeting at such an early stage.

"We both have to deal with it. I'm sure he's not thrilled about it either," said sixth seed Roddick, who is locked at 3-3 in previous meetings with Safin.

Defending champion Roger Federer faces his first genuine test when he plays Russian 25th seed Mikhail Youzhny, the man who upset Rafael Nadal en route to the U.S. Open semi-finals last year.

The Swiss master has only lost two sets in seven encounters against the 24-year-old Muscovite, but he recognises the talented all-rounder is a potential banana skin.

"He upset Rafa at the U.S. Open. I've played him several times and know what a great player he is. Got to make sure I get through that one first," the top seed said.

If successful, Federer is then likely to play in-form Serb Novak Djokovic in the fourth round if, as expected, the 19-year-old beats Asia's final representative in the men's draw, Thailand's Danai Udomchoke.

France's Amelie Mauresmo, the second seed, continues the defence of her title against Czech world number 83 Eva Birnerova.

Twice former champion Serena Williams, unseeded this year due to a catalogue of injuries, gets her chance to put the cat among the pigeons against fifth-ranked Russian Nadia Petrova.

Third seed Svetlana Kuznetsova akes on fellow Russian Maria Kirilenko, the 26th seed, for a place in the fourth round and at least one unseeded player will make the last 16 when the Czech Republic's Lucie Safarova plays Anastasiya Yakimova of Bulgaria.