IT SEEMS a very long time ago now that Boris Becker, the defending Australian Open champion, hit a desperately-tired backhand into the tram lines and Carlos Moya jerked his arms high above his head in acknowledgment of a famous five-set, first-round victory.

Nobody would have been the least surprised if the 20-year-old Spaniard, playing only his fifth Grand Slam tournament, had quietly disappeared on some outside court during the next few days. He had made his mark by assassinating the king.

Now, having survived a further five rounds, Moya steps out tomorrow on centre court to take on Pete Sampras in the match of his short tennis lifetime.

American Sampras has been in 10 Grand Slam finals and won eight. He has a career total of 44 singles titles. Prior to his remarkable run here, Moya had never progressed beyond the second round in Melbourne, Paris, London, or New York and has just two titles to his name. The gulf is huge.

Yesterday afternoon, just after Sampras had beaten Austria's Thomas Muster 6-1,7-6,6-3, Moya sat in one of the small restaurants just outside Melbourne's impressive centre court.

With his hair tied back off his face, he leaned his elbows nonchalantly against a table and gave an informal interview to an American journalist. Barely anyone gave him a second glance; some may not have even recognised him.

There are always upsets in the Grand Slams, and there was a huge scattering of seeds last year, notably at Roland Garros and Wimbledon. Yet there has been something particularly romantic and rewarding about Moya's success, not least because he has played such tantalising tennis.

As Sampras said yesterday, it takes a pretty remarkable performance for anybody to beat Michael Chang in straight sets, and Moya achieved it with daring and elan.

"It should be a good fight between me and Carlos. He's obviously been playing at a very high level. We have not met before and I'm looking forward to it," Sampras said.

Last year was a difficult one for the American, with the death of his friend and coach Tim Gullikson in May. Until the US Open at Flushing Meadow, Sampras had not won a Grand Slam, but in the final he defeated Chang in straight sets. He then took the ATP Finals title in Hanover and retained his end-of-season number one spot for the fourth successive year.

Muster, after convincing victories over Jim Courier and Goran Ivanisevic here, had been expected to give Sampras a severe test and, indeed, the contest was much closer than the scoreline suggests. But Sampras was back to his dominating best, moving Muster around the court, rarely allowing him to settle and throttling him with an array of masterful forehands and severe volleys.

The Austrian, who also reached the semi-finals here in 1989 when he lost to Ivan Lendl, grunted, whistled, puffed, and wheezed like a demented steam boiler, occasionally beating Sampras with passes at the net of the most supreme quality.

Muster is so much more than a mere action-man, even if he does resemble a squaddie on manoeuvres and by the American's own admission, Muster should have won the second set after breaking Sampras for a 4-2 lead.

Sampras was mightily relieved to break back, punching the air in relief, and then taking the tie-break with some ease.

The first point was notable for a 30-stroke rally; Muster loves to keep the ball in play, but throughout the match, Sampras rallied with equal zeal and invariably came up with the winning shot.

Muster is always hard on himself when things are going wrong. At the end of the tie-break, and during the final set, his head rocked and rolled in frustration, and it seemed as if all life's cares had descended on his broad shoulders.

Yet at the end, he put his arm around Sampras's shoulders in an obvious gesture of recognition that the better man had won. And later, he was equally generous in defeat, acknowledging that the American's all round game was the best in the world.

"I think I set the tone for the match in the first set, but it was always going to be toe to toe against Thomas," Sampras said. He feels his own form is getting better and better, while being fully aware that his worst moment came during his fourth-round match against 19-year-old Dominik Hrbaty of Slovakia, who took him to five sets.

It is perfectly possible that Sampras will wipe the floor tomorrow with the inexperienced Moya, who was beaten in two sets by Tim Henman in the Sydney international final just before the Australian Open started.

"The top players are human and they make mistakes," said Moya. He also knows that the difference between Sampras and the others is that even when the American plays badly, he invariably wins.