Greg Rusedski has always had one of the biggest smiles in sport.

But after a year when he had precious little to smile about, last night in Melbourne it was wider than ever.

Unseeded and unfancied even by himself, Rusedski pulled off the best win of his life to send world No 1 and top seed Gustavo Kuerten crashing out of the Australian Open.

''I'm more surprised than anybody, but I'm going to cherish this moment,'' he said, for once permitting himself a celebration in the middle of a tournament.

''It's my greatest victory by far. I've never beaten a No 1 player in the world on a stadium court at a Grand Slam.

''I've proved I'm a player again and it's a great feeling. I could not ask for more than to play such a fantastic match against the world No 1.

''There's a lot to look forward to now. And I'm going to enjoy tonight.''

Even if he goes no further he will depart a happy man. But the 27-year-old should go further - his opponent for a place in the last 16 is German qualifier Lars Burgsmuller, ranked 185th in the world.

If he comes through that, 15th seed Arnaud Clement or Switzerland's Roger Federer will not fancy playing him on the form he produced against top seed Kuerten.

It was a match that for drama, excitement and emotion will be hard to beat.

The drama played out before a 14,000 crowd under the night lights of the Rod Laver Arena, saw Rusedski fight back from match-point down to reach the third round 4-6 6-4 6-3 2-6 9-7.

The emotion was played out inside the Montreal-born player, whose tennis world fell apart last season as injury after injury, combined with a total loss of form and confidence, left him not knowing when his next victory was going to come.

Before last night's duel, Rusedski held a 3-1 advantage in matches between the two but the last of those was two years ago and their career paths have gone in totally different directions since then.

A first-round loser at Wimbledon and the French Open last year, Rusedski got through only one match at the US Open and, like Tim Henman, lost his opening game at the Sydney Olympics.

By the time he arrived in Melbourne he was down in 65th place in the world rankings from a high of fourth just after he reached the 1997 US Open final.

There was nothing in his four-set struggle against South African qualifier Marcos Ondruska out on Court Three to hint at what was to follow.

But Rusedski relished the bigger stage and thrived in the ''nothing to lose'' role of the massive underdog. The pressure was all on Kuerten.

The Brazilian was handling it fine as he took the opening set, but when Rusedski's serve started firing on all cylinders like the good old days it was a different matter.

The odds were still on Kuerten to win when he levelled in the fourth, and when Rusedski was on the wrong end of two bad line calls - one of them horrendously bad - it seemed he was destined to come off as a gallant loser.

Kuerten had his match point at 6-5, but netted a return and was broken in the next game.

Rusedski, serving for the match, was broken back. But incredibly, from love-40 he won nine points in a row and the ninth gave him a famous victory.

New coach Pat Cash had told Rusedski to expect the changes he is making to his serving action - designed to ease the stress on his suspect back - to take three months to become effective.

''That's why I'm so surprised,'' he said. ''We're still in the building process and I feel I can get better.

"That's a frightening thing to say when you've just beaten the No 1 player in the world."

There was another match that came close to Rusedski's in terms of thrills.

Unseeded German Tommy Haas led seventh seed Lleyton Hewitt 5-0 in the first set, 4-1 in the second set and 4-2 in the third.

Yet the 19-year-old Australian won them all, the first most remarkably of all by winning seven games in a row.

In the women's singles, there were easy wins for Martina Hingis, Serena Williams and Mary Pierce, a slightly harder one for Venus Williams and defeat for 16th seed Amy Frazier to Italian Rita Grande.