It had to be these two.

Rafael Nadal is No. 1, Novak Djokovic is No. 2. They won three of the four Grand Slams between them this year, and either Rafa or Nole appeared in all four major finals. Perhaps even more impressively, they won eight of the nine Masters 1000 events. For good measure, they also staged what may have been the two best matches of the season, in Paris and Montreal. To make any kind of sense, this London final, which is also the grand finale of the ATP’s season, had to have Rafa and Nole across the net from each other.

Now that they’ve made their way—undefeated, of course—through the rest of the tour’s Top 8, who is going to win? I submit that there is no way, really, to say. Even Djokovic has no idea.

“There’s no clear favorite,” he said in his post-semifinal press conference on Sunday.

But Djokovic is anticipating one thing. “It’s expected we go the distance,” he said.

It’s true: This is one of the very rare tennis matches where I’d actually be surprised if it didn’t live up to its hype

Nadal has a 22-16 head-to-head record against Djokovic. This year he’s won three of their five matches, including the two biggest, in the U.S. Open final and the French Open semifinals. But Djokovic won their last match, in Beijing on hard courts this fall. More important, since he lost the U.S. Open, and the No. 1 ranking, to Rafa, Djokovic seems to have been liberated. He’s the hunter again, rather than the hunted, and that psychological shift has helped him win 21 matches, three tournaments, and two Masters events in a row.

Until this event, I thought Nadal, since winning that Open final, had exhibited some of the symptoms of the hunted. Or at least he had exhibited some of the symptoms of a player who had virtually locked up the year-end No. 1 ranking, but still had tournaments on his schedule, tournaments that didn't qualify as big titles for him. But there is still one big title for Rafa: this one. Nadal has never won a World Tour Final, and has only reached the final one other time. He must feel like this could be the best chance he’ll ever have to do it. Unlike the rest of the fall, in London Nadal has played as if he has a title to win, rather than a ranking to hang onto. Still, Djokovic’s motivation will also be high. He can’t finish the year No. 1, but this is a chance for him to win a third World Tour Final, get a measure of revenge for his U.S. Open defeat, and send a message to Rafa that in 2014 he’ll be right there with him—and that, at his best, he still has the advantage in their matchup on hard courts.

As far as form goes, there’s not much to choose between them there, either. Nadal played his smartest and best match of the tournament against Roger Federer on Sunday, while Djokovic was as solid as ever in making routine work of Stan Wawrinka. Neither gave their Swiss opponent much hope. If there’s one shot that could make a difference, it’s Nadal’s forehand. He needs to be able to take it down the line against Djokovic, and he did that extremely well against Federer today. One unknown is the serve. Nadal used it effectively, without going for too much, against Federer today. Can he do the same to Djokovic, who is a much more dangerous returner?

How about the confidence factor? As always, that will play a role. The biggest difference between their matches in 2011, when Djokovic was winning them, and 2012-13, when Nadal has mostly come out on top, has been the Serb’s level of belief. In 2011, Djokovic became the first and so far only player to sincerely convince himself that he could outlast Nadal in rallies. Because of that, he was content to be patient and not rush for winners. More recently, Djokovic hasn’t had that same confidence, and he has rushed for winners. But belief works both ways. If Djokovic gets into baseline patterns that have worked for him in the past—backhand cross-court, backhand up the line into open court—will Nadal get discouraged and start reliving those memories of 2011?

Historically, Nadal has taken advantage of his chances to win big events for the first time. He won his first French Open final, first Australian Open final, and, in 2010, his first U.S. Open final to complete a career Grand Slam. But Rafa's experience was different at the WTF. He lost his only final here, to Federer, in three sets, in 2010. This year Rafa seems to be on a mission to put his past at this event behind him and get a win while he’s healthy and playing well. While I think this is truly a toss-up, and while I wouldn’t be surprised if it went the other way, I’ll take Nadal to complete his most complete season with one more win.

The Pick: Nadal in three sets