It isn’t supposed to end this way. The World Tour Finals was conceived to finish things, settle arguments, determine a crystal-clear pecking order dictated by a big computer humming away in some climate-controlled basement. It’s designed to produce finality. The World Tour Finals is, at least in theory, a loose-ends tyer-upper.

But the only loose ends tied up in London were the stray hairs perpetually escaping the headband of David Ferrer, who never made it out of the round-robin stage.

Instead of “game over” for another year, the resonant message in Novak Djokovic’s 6-3, 6-4 triumph over Rafael Nadal was “Game on!” As many answers as the match posed about 2013, it planted that many questions for 2014. It’s as if the spell that some evil sorceress (perhaps named Xisca?) had cast over Djokovic shortly after his wildly successful 2011 campaign was suddenly broken in early September, after Nadal hammered his Serbian rival into submission on a hard court at the U.S. Open.

Suddenly, Djokovic’s eyelids flew open, he sat bolt upright, and, as he ran out the door and down the street pulling on his shorts, he shouted, “Holy cow, that guy just took off with my ranking!”

The improbable thing is that Djokovic actually caught up with the thief on the last day of the tennis year, albeit too late to get back what had been taken from him.

The whole scenario is kind of funny, or it is if you’re not so ga-ga for either or both of these guys that you’ve lost your sense of humor. When Djokovic dominated in 2011 there was much weeping and gnashing of teeth in the Nadal camp; it remained that way right through the early part of 2012. But then the skies cleared for Nadal during his beloved clay-court season, and he counted coup on Djokovic in the French Open final.

However, tragedy struck at Wimbledon. While closing quickly on his top-ranked rival, Nadal was blasted off the court in the second round by a Czech journeyman ranked No. 100. Nadal promptly disappeared to tend to his aching knees and didn’t return until early this year—February, to be exact.

Nadal began to roll up the wins immediately upon his return early this year—all the while reiterating fears that he might never play at a decent level again. Perhaps Djokovic took it all in and told himself there was no way a guy who had missed seven months and the first major of the year could win 10 tournaments, including two Grand Slams, and finish No. 1.

Whatever the case or reason, a cavalier quality crept into Djokovic’s game. As sins of top players go, that’s a rare but deadly one.

It’s been clear throughout the rise of Djokovic that he’s well-suited for the role of tennis icon. Somehow, he seemed to grow at the same rate as his reputation. He matured into the role, accepting the pressures and responsibilities of a No. 1 player with grace and dignity. He took it lightly—perhaps too lightly—from about the time he mastered Nadal again in that epic Australian Open final of 2012.

If there’s such a thing as loving life a little too much, Djokovic may have been guilty. At times through portions of 2012—when Roger Federer was in resurgence, and Andy Murray’s star was climbing—and then during first three-quarters of this year, Djokovic seemed to take losses a bit too philosophically. He was unperturbed, especially while Nadal gradually and inexorably closed the gap.

All that seemed to change with Nadal’s win over Djokovic in the final of the U.S. Open just two months ago. It was a stinging rebuke of Djokovic’s modus operandi, and it finally did what no mangled smash from right on top of the net or lackluster service return on break point could—it seemed to alert him to the degree of danger he faced. With that U.S. Open title, Nadal came within striking distance of Djokovic’s top ranking. And it turned out to be too late for Djokovic to do very much about it. How does a guy who’s No. 1 at the conclusion of the U.S. Open win 22 matches in a row—and still fall to No. 2, the way Djokovic did this fall?

I’m sure that at some point in the celebration of his win over Nadal in London, the smile on Djokovic’s face contained a trace of irony, if not exactly bitterness.

A lot will be said about Nadal’s shortcomings on indoor hard courts, and there certainly are concrete, game-and-surface based reasons for why this spectacularly great player has never won the year-end championships. But to my mind, the result was heavily influenced by the amount of skin each man had in the game.

Given what Nadal went through during the second half of 2012, his year was successful to a degree that nobody would have dared predict. Even Nadal declared when he won the French Open for the 45th time in a row back in June that the victory had made his year, come what may. What came was even greater success, as Nadal compiled a 75-7 record for the year (with two Grand Slams and 10 total titles). That compares pretty well with Djokovic’s 2011 season, during which he went 70-6.

To top off his comeback, Nadal clinched the year-end No. 1 ranking just two matches into this World Tour Finals. Could you have dreamt up a better way to make this final with Djokovic seem more exhibition than Armageddon?

“Futile” probably isn’t the right word to use when it comes to characterizing Djokovic’s manic, wonderful drive to fight Nadal to the bitter end this year. He played throughout the autumn like a man with a point to make, and the string of wins that streamed from his racquet (two of them over Nadal) made it eloquent. It continued to make it right up until the moment Djokovic ran out of year.

Going into the final, Djokovic knew that Nadal’s motivation could not have been at its highest level once he clinched the year-end No. 1 ranking. But then, Djokovic’s own degree-of-interest had just as much if not more reason to wane once the rankings issue was decided. What Djokovic showed on Monday night in London was not just a lethal, overwhelming game, but a deadly, awe-inspiring pride.

Djokovic was playing to defend his title, and it’s a significant one that ranks right behind the Grand Slam events. Almost as important, even if he didn’t look at it this way, is that he stopped Nadal’s drive to join that club of season-ending champions and continued to water the seed of doubt planted in the Spaniard’s mind about indoor tennis and, in particular, this tournament.

Djokovic also wrote a coda that, while it will not spoil the satisfaction Nadal takes out of this spectacularly successful comeback year, certainly will provide the introduction to 2014. The World Tour Finals this year wasn’t about resolution or finality, it was about pride, and a rivalry that might just now be entering its greatest phase.