photo by Ben Solomon for the New York Times

And that is how it ends, and how this begins.

It – the unofficial close to the finest of the Roger Federer and Rafael Nadal rivalry, and this – tennis’ new feud between Novak Djokovic and Nadal.

We will see more of the former, of Rafa and Roger battling, of epic five-setters that tick past the 4:00 mark, yet not at the levels we’ve seen. This tournament finally confirmed what we’ve seen all year.

But this, what is this? And who were they?

This was not the Rafa of old in New York, and it certainly wasn’t the Djokovic of old in… anywhere.

We’d seen Rafa do all of this on Australia’s hard courts or on France’s red clay or on Wimbledon’s green grass, but never in New York.

On Monday night, Rafa showed a few nerves, backing off when he normally steps forward. He even lost more than one service game (gasp!). But somehow, Rafa kept up his ridiculous serving, mixing speed and spin perfectly and won the last Grand Slam he hadn’t dominated.

He’s 24. He has won nine Grand Slams. That’s one more than Andre Agassi won his entire career.

For Djokovic, we saw this Down Under more than two years ago, but not much since. Certainly, we had never the competitor that we saw him become during the last two weeks. From his first match of the 2010 U.S Open, when he was down a set and a break, to his semifinal against Federer, when Djokovic was down two match points, Djokovic accessed a level of tennis we didn’t know he had and maybe he didn’t know he had, either.

In the process, he went from the hated, always hurt, always complaining Novak Djokovic in New York to the endeared, playing with pain, no excuses Novak Djokovic, cheered by New Yorkers.

Oh, yeah. He’s 23.

A new rivalry was born Monday. No, the final wasn’t quite the classic Djokovic’s second set falsely foreshadowed. But it was some sort of classic, something that we’ll remember for it being the start of something better.

And this how another classic U.S. Open ends: the one on his way to becoming the best ever enjoys the best year ever as one of the best shows he can legitimately battle the ultimate champion.

Next time a buddy of yours wants to watch the game with a different group of friends or just wants to be away from you for awhile, call Novak Djokovic, who declared himself the ultimate party crasher this afternoon when he took out Roger Federer 5-7, 6-1, 5-7, 6-2, 7-5.

Has there ever been a more anticipated, more talked about match that didn’t happen? Analysts such as Brad Gilbert were spouting out all sorts of predictions, saying a Roger Federer v. Rafael Nadal U.S. Open final would be the best match in tennis history. If Rafa would have won, best year ever.

Somebody forgot to let Djokovic know about all this hype, or he just didn’t care. Or, the more likely scenario, all of this Rafa-Roger talk let Djokovic play pressure-free and loose. It let him rip service returns back to Federer, and smash forehands as if he were still warming up.

We’ve seen Federer show his human side for a few years now. But the way Djokovic took out Federer and denied him his seventh straight U.S. Open final is something we still don’t see that often.

Two times Federer had match points today against a rattled Djokovic during Djokovic’s 4-5 service game in the final set. During the first point, Djokovic, in control of the point, struck an overhead. Federer returned it, forcing Djokovic to hit another one, only Djokovic duffed it into the net.

Then came back that feeling, the calming feeling that tells you, oh, here we go, now Federer has it. That was fun while it lasted, but time to hit the ol’ switch again, break Djokovic here and play Rafa tomorrow.

The game tally racked up to 15-40. Yep, match about over.

Then, during the biggest-pressure moments of the year and maybe of his career, Djokovic showed aggression and didn’t let the fear debilitate him. He attacked Federer, darted to the net and hit a “gutsy” swinging forehand volley.

Two swings into the next point, he crushed a forehand crosscourt, out of Federer’s reach. “Unbelievable!” screamed CBS’ Dick Enberg.

Right there, Djokovic had won the match. He held, broke Federer, then held, giving us the best match of this fantastic U.S. Open.

But of all the people to take out Federer, Djokovic? Really? After he barely showed any desire for tennis in Cincinnati, falling 6-4, 7-5 to Andy Roddick, who was just getting over mono? After Djokovic had to come back from being down 2-1 sets and a break against Viktor Troicki in the first round of the U.S. Open?

Now, of course, he faces Nadal. (Congratulations, Novak!)

Nadal’s serve has looked better than ever. He’s won 89 of the 91 games he has served. The claim that these New York courts were too fast for Rafa is almost laughable after seeing him not drop a set in his first six matches.

A victory Sunday gives Nadal a career Grand Slam and his ninth major. He would become the first man to win the French Open, Wimbledon and the U.S. Open in the same year since Rod Laver did it in 1969.

What a party to crash.