As confetti rained down on the Arthur Ashe Stadium at Flushing Meadows, with Novak Djokovic holding aloft that famous silver cup, Roger Federer, standing beside him, would have wondered just how he let it all slip away.

In a US Open 2015 final that promised so much, we were left a little disappointed. Yes, we got to see Djokovic's ridiculous fighting qualities, that ability to counter-punch like nobody else in the sport and that amazing skill to always come up trumps in the big points.

However, we did not get to see the Federer that we have seen so often in these major finals. There was no glide across the court to hit winner after winner, no delectable forehands that always found its spot and no serve and volley tennis that has come to define this newly-refined Roger Federer.

The only thing that did not let Federer down in this US Open 2015 men's singles final was his backhand, but against a player like Djokovic, without any doubt the best men's player on the planet, just a good backhand will not do – the forehand needs to be perfect, the serves need to be on point and those volleys need to throw Djokovic off his game.

Djokovic was not at his absolute best either, not like in that Wimbledon final a couple of months ago, and that is precisely why Federer will look at this match as a lost chance at finally getting out of that 17 Grand Slam titles zone.

The amount of chances Federer had in this match cannot be counted without a calculator – so many times Djokovic left the door ajar, and all it required was for Federer to push through and walk right in. Instead, the world number two rang the doorbell and waited for Djokovic to invite him in, and that was never going to happen was it.

Djokovic does not do throwing-away-matches, you need to beat him, every single time, and when it mattered most, Federer could not produce the goods to knock the stuffing out of the Serbian.

There were moments when Djokovic looked like he might get knocked out – in the first set, for instance, the world number one lost his balance and came crashing down on the court, skinning his right hand, elbow and knee, but Federer, apart from a few points after that, could not take full advantage.

In the third set, there were moments when Djokovic looked lost, with the partisan crowd who wanted Federer to win, getting to him a little bit; but, again, the Swiss could not find those right shots, missing easy forehands, which on any other day he would have put away with his eyes closed.

That third set will haunt Federer; he should have won it with a couple of breaks. However, Djokovic hung on and actually took the set 6-4. With his spirit broken, Djokovic, smelling blood, went for the kill, and even if there were a few Oh-Federer-might-come-back-you-know moments in the end, the result was never really in doubt, not after Federer let that third set slip away.

It might have been an absolute classic had Federer really found his range, because, you know if Federer had raised his game, Djokovic would have answered in kind as well. However, it was not to be, and while the drama and theatre was quite high, this US Open final will always be in that "if only" category, particularly for the Swiss master, who will know he should have really been the one lifting that trophy.