DERBY DAYS TENNIS:In four seasons, Federer and Nadal have divided 14 of the 16 Grand Slam title between them, but they have never met at any round of the Austrailian Open, writes DAMIAN CULLEN.

LIKE GOOD wines, rivalries grow better with age. The aftertaste can revive memories of a rich, spicy and elegant blend – with plenty of character of course.

The 80 meetings (60 in finals) of Martina Navratilova and Chris Evert is considered by many to be one of the greatest match-ups in tennis or, indeed, any sport. Similarly, any combination involving Jimmy Connors, Bjorn Borg and John McEnroe is surely among the greatest on the men’s side.

Each dual may have been appreciated at the time, but time has enhanced their bouquet greatly.

But it seems there is often a tendency not to fully appreciate more recent vintages.

Perhaps this is why the duals between Roger Federer and Rafael Nadal – which began at the 2004 Miami Masters – have not already been recognised as the greatest tennis rivalry of all.

It was the year Federer took the tennis world by storm, winning three of the four Grand Slam tournaments, and not losing a single match to any player ranked in the top-10.

By the end of 2004, International Tennis Federation (ITF) officials were anxiously awaiting someone to challenge the Swiss player’s almost total dominance of the men’s game.

That March, the top seed met a 17-year-old Spaniard in the third round of the Miami tournament, with Nadal winning in straight sets. At the time, no one dared presume a challenger had been found for the Federer Express. Excuses for the shock loss were reached for and quickly handed out. And, 12 months later, the two met for a second time, at the same event – this time on the final day.

After losing the first two sets, Federer sneaked the third on a tie-break, and claimed the final two to revenge the previous year’s result.

A rivalry was born.

Since that day early in 2005, Federer and Nadal have met 16 times on the circuit – with the record, incredibly, reading 12-6 in Nadal’s favour.

While the meetings have not been dominated by the surface they’ve played on, the matches have been heavily influenced by the court’s appearance. With the players so evenly matched, outside influences have had a huge bearing on each contest.

During the past four seasons, Nadal has established himself as the king of clay. Ten of the meetings between the two have been on clay, with Nadal winning all but one – Federer’s win in the 2007 Hamburg Masters ended the Spaniard’s record, 81-game claycourt winning streak.

Federer, however, has held the edge on hardcourt, and, until Nadal’s victory in that sensational, five-set Wimbledon decider last season, completely dominated on grass.

It was perhaps fitting Federer would bring Nadal’s record streak on clay to an end, as Federer holds the record for consecutive victories on grass (61) and hard courts (56); both times, it was Nadal who ended the winning runs.

But Nadal was never simply a thorn in Federer’s side. In 2006, Federer would have claimed his first Grand Slam if it had not been for Nadal’s victory in the French Open.The most famous claycourt in the world was Nadal’s playground.

The following year, Federer again won in Melbourne and New York, and again prevailed over Nadal in the Wimbledon final – this time needing five sets and all his skill to prevail on grass. However, once again he was denied a clean sweep by Nadal’s prowess on clay.

And last season, after a hat-trick of victories in Les Internationaux de France de Roland Garros, Nadal went one further and, in one of the greatest matches, defeated Federer on grass for the first time.

That was the final piece in a new three-piece jigsaw in men’s tennis – it is now Nadal, Federer and the rest.

They have made the top rankings on the ATP Tour exclusively theirs since July 2005, with Federer finally knocked off the number one spot last August.

And, in four seasons, Federer and Nadal have divided 14 of the 16 Grand Slam titles between them, with Marat Safin in the 2005 Australian Open, and Novak Djokovic’s victory in last season’s edition, the only crowns to have escaped their collective grasp.

However, despite all that, they have never met at any round of the Australian Open.

Last season, top seed Federer lost in the semi-final to the eventual winner Djokovic, while Nadal slipped up at the same stage to Jo-Wilfried Tsonga.

With Andy Murray and Djokovic now out of contention, Nadal will take on sixth-seed Gilles Simon of France in the quarter-final today (8.30am Irish) to decide who will face either Spain’s Fernando Verdasco or France’s Tsonga in Friday morning’s semi-final.

Federer has already reached a record 19th major semi-final in a row, and will face Andy Roddick tomorrow morning.

A Nadal versus Federer decider on Sunday is far from certain, even if it is the match-up most fans crave.

But even if they don’t meet this weekend, they will surely face each other a half-dozen times before they’re done with 2009.

Enough to give connoisseurs a regular kick from the game’s champagne match-up. Rare enough to remain an excellent vintage.