THE tennis world has always loved its rivalries. In the early 1980s, it was John McEnroe slowly stealing Jimmy Connors' crown via a series of games that were played amid a backdrop of mutual dislike.

By the end of the decade, Boris Becker and Stefan Edberg had assumed centre stage, trading athletic blows at the top of the world rankings.

And in the 1990s, Pete Sampras and Andre Agassi met 34 times as the former's attacking style clashed with the latter's formidable defence.

Now, after this month's Italian Open final - a match that is already being lauded as tennis' moment of the Millennium - there is a new contest in town.

After three years of almost uninterrupted success at the top of the men's game, world number one Roger Federer has a rival to his crown.

In 19-year-old Rafael Nadal, tennis has discovered a teenage prodigy able to compete with the master.

Over the course of the next decade, the duo look like developing a rivalry that can elevate both to the level of all-time great.

Federer, of course, can already claim to be just that. He currently holds the Wimbledon, US Open and Australian Open trophies, has already won seven Grand Slams and was recently named World Sportsman of the Year at the Laureus Sports Awards for the second year running.

He has been world number one for the last two years and is the only player to have won four Masters Series titles in the same calendar year.

Just recently, though, the 24-year-old has been getting a little bit scared.

Last weekend, he lost 6-7, 7-6, 6-4, 2-6, 7-6 to Nadal in the final of the Italian Open.

The game, a brooding five-set epic that lasted six minutes more than five hours, would have been remarkable whatever the outcome.

That it ended with Nadal having extended his unbeaten run on clay to a record-equalling 53 games meant it will go down in the history books as the moment Federer's shroud of invincibility was removed.

Federer does not lose very often, but he never loses having had two match points and having led the decisive fifth set 4-1.

That, though, was exactly what happened in Rome. The Swiss star was a point away from leading 5-2 when Nadal forced him into an error so uncharacteristic it drew grasps from the startled crowd.

Leading in the decisive tie-break, he could only watch aghast as his opponent produced a formidable forehand winner.

At 5-3 ahead, he watched two points slip away as extended rallies ended with him drilling forehands into the tramlines.

A minute later, and the game was up.

Federer, the arch-competitor, had been ground down by a clay-courter who now appears invincible ahead of the French Open that begins in Roland Garros on Monday.

To make matters worse, it was the fifth time in six games that Nadal has brushed him aside and, as he is still a teenager, it should be assumed that the Spaniard can only get better.

He cannot, however, become any more competitive. While Nadal's skills are not in doubt, particularly his scorching forehand, it is his boundless energy and unwavering consistency that make him such a formidable opponent.

Federer does not make many mistakes, yet compared with Nadal he looks errorprone.

The Majorcan's groundstrokes are formidable - he leaps from the ground to play over the ball at every available opportunity - but, just as significantly, they are as reliable in the fifth hour of a match as they are in the first.

Frew McMillan, a doubles expert in the 1960s and a commentator today, has repeatedly decried Nadal's lack of finesse, but even he is impressed by his incredible durability.

"He is not a silky performer, " said McMillan, "but he astonishes in his powers of retrieval. He has eliminated his errors and, when he needs to accelerate, he can lower the trajectory of his shot to hit the outright winner."

With the help of modern technology, and particularly on clay, that is more than enough.

The question Nadal must now answer is how to transfer that style on to the game's other surfaces, particularly grass.

In the past, leading clay-courters would simply have ignored it. Ivan Lendl was never involved in a year-long rivalry because, in the summer months, he might as well have kept his racket in its bag.

Nadal, however, is different. Despite his Majorcan upbringing, he has a "dream" of winning Wimbledon, a prize he considers to be more valuable than any other.

This summer, rather than booking a hotel room for a day at a time, he has rented a house in London in the hope that he will need it for the best part of a fortnight.

Some would call it over-confidence, others would term it arrogance. Ultimately, it is merely the action of a man who is convinced he will be Federer's equal for many years to come.

ENGLAND'S B team play Belarus this evening in a game that is likely to tell us much about what might happen if things go wrong in the run-up to the World Cup finals.

With friendlies against Hungary and Jamaica to come next week, Sven-Goran Eriksson has wisely decided to give his fringe players some match practice ahead of next month's tournament.

And, despite most critics bemoaning the lack of depth in the England squad, this evening's line-up gives plenty of cause for optimism.

Sol Campbell and Jamie Carragher would get into most international sides, while Stewart Downing and Aaron Lennon are unknown but exciting quantities on the flanks.

Attack is a problem - Michael Owen and Peter Crouch will be England's A team in the absence of Wayne Rooney - but Eriksson cannot claim he does not have the players to make a difference if things are not going to plan next month.