It will be the 19th career meeting between Rafael Nadal and Roger Federer when the top two players in the world square off in a dream final on Sunday night at the Australian Open.

Nadal is dominating the head-to-head series 12-6, but eight of those wins have come on clay, Nadal’s favorite surface and Federer’s least preferable. The most recent meeting, of course, came in the memorable 2008 Wimbledon final, where Nadal outlasted then-No. 1 Federer 9-7 in the fifth set.

The hard courts of Melbourne will be the most neutral surface yet for what will be Federer and Nadal’s seventh meeting in a Grand Slam final. Federer beat Nadal in two Wimbledon finals prior to last season’s defeat, while Nadal has conquered Federer for three of his four French Open titles.

Now that Nadal has overcome Federer on the Swiss’ favorite surface (grass), if he can get the best of Federer on hard courts as well, he will be the clear-cut dominant player in men’s tennis. But Federer is starting to look like the Federer of old. An enormous struggle with Tomas Berdych in the fourth round seemed to wake Federer up from a relatively lackluster first week of the tournament. In the quarterfinals Federer destroyed Juan Martin Del Potro 6-3, 6-0, 6-0 and in the semis he cruised past Andy Roddick 6-2, 7-5, 7-5.

His win over Roddick came on Thursday, so Federer has had one more extra day of rest than Nadal. During that extra day, he got to kick back and relax while his adversary contested the longest match in the history of the Australian Open: a grueling 6-7(4), 6-4, 7-6(2), 6-7(1) win over fellow Spaniard Fernando Verdasco. It was Nadal’s first real test of the fortnight. Nadal reached that spot in the tournament by taking out Christophe Rochus, Roko Karanusic, Tommy Haas, Fernando Gonzalez, and Gilles Simon all in straight sets.

But now Nadal—after rolling along through five matches—most certainly has to be fatigued after the five hour and fourteen minute slugfest against Verdasco.

Nadal himself admits that he is unsure how his body will hold up physically for Sunday night’s blockbuster title match. “Little bit unlucky,” Nadal said when asked how exciting it was to finally play Federer in hard-court major final. “Don’t know how I gonna be for the final. I gonna try my best for sure for recover my body and my physical performance. But, you know, after one match like this, the next days you feel much heavier.”

Verdasco agrees. “Is also a pity that…he played that long match for the final, when Roger played one day before and a much shorter match,” he said. “I want him to be 100% to play that final and to try to win. He’s a big friend. I wish him the best of luck in the final. I hope that he will win.”

But Nadal is not making any excuses about only getting one day of rest, whereas Federer gets two. “The US Open was for both players the semifinal the same day,” he noted. “Here is the only tournament is not like this. But, you know, you still have one day off. So that’s the sport.”

The Spaniard even pointed out that he would have had the advantage last year, but both he and Federer lost in the semifinals. “But (it) is like this. Last year I played on Thursday. I lost. I didn’t play the final. But, anyway, I play on Thursday, and Roger play on Friday.”

So Nadal says the playing field is fair, and if so, with a fair field and neutral surface, this should make for one of the most (if not THE most) intriguing and highly-anticipated match in tennis history.

Why? Consider: the 2009 Australian Open title is far from the only thing only the line. You know, there’s that thing called the all-time Grand Slam record for most men’s singles titles. Well, as every knows, Pete Sampras owns 14 majors and Federer stands just one behind. A win would not only give Federer a tie, but it would set him up well to take the record outright at Wimbledon this summer (assuming Nadal wins the French again).

Should Federer lose, there is a remote chance he might never pass Sampras. Nadal would solidify himself as the dominant man on all three surfaces, and with Andy Murray (among others) on a rapid rise, Federer’s chances at Grand Slams—while still great—are getting slimmer and slimmer as opposed to better and better.

For Nadal, at stake is his sixth Grand Slam. We can start putting him in the Greatest Of All Time discussion if he prevails on Sunday. In addition to owning six majors, he will have won three of the four slams. All that’s left would be the U.S. Open, meaning he would be just one away from the career Grand Slam, most recently accomplished by Andre Agassi at the 1999 French Open. Sampras never did it (failed to win the French Open) and Federer still hasn’t done it (also has never won the French). This is clearly up for debate, but I’d say the chances are Federer will retire having never captured the title at Roland Garros.

If Nadal can win on Sunday and somehow win the U.S. Open (which is a decent probability, considering Nadal will probably still be going strong when Federer is over the hill once and for all), he will retire—whenever he does—with the career Grand Slam. That gives him a leg up on Federer, and so does his Olympic gold in men’s singles, which he won this summer.

While all of that is speculation, this isn’t: it does not get any bigger than Sunday’s Federer-Nadal 2009 Australian Open final.