NARROW margins.

Slender slivers of skill that separate success from second best at the highest level. We have seen them make the difference before in matches between Roger Federer and Andy Murray - not always, it should be said, in the former's favour - and we saw them again in this semi-final as the Swiss player prevailed in three sets.

As Murray himself said afterwards, although he could not say for sure if that was the best he had ever performed in a straight-sets defeat, he knew he had certainly not played particularly badly. In fact, by the standards of ordinary mortals, he had played outrageously well - and yet it was not enough even to break his opponent's serve.

The closest Murray came to doing so, in fact, was in the very first game. After that, Federer's serve was simply too good; indeed, perhaps the best it has ever been.

By contrast, Murray was vulnerable on his second serve, as he had been in a couple of his previous matches. There is an argument that it is that aspect of his game that prevents him from being quite on the same level as Federer and Novak Djokovic, but it is hard to tell if is an argument that has any use. After all, accepting that your second serve is letting you down is one thing: doing something about it is quite another. It's not as if Murray is unaware of his shortcomings, such as they are.

The frustrating thing, the aspect of the fortnight that made this match feel anti-climactic for Murray's supporters, is that for some time he has been better than nearly every other player on tour, yet not quite good enough to match the two men who will now contest Sunday's final. Murray's first five matches - even the one against 6ft 11inch Ivo Karlovic - had been so straightforward that they felt like little more than limbering-up exercises. So there was no severe tension in them, no real fear that he would lose, no death-or-glory drama.

The Federer match felt like the real thing at last: a clash of two genuine heavyweights of the game. Here, from the start, there was tension, and excitement - and for the first time a significant number of opposition fans. Small cantons of Swiss supporters were dotted around Centre Court, identifiable by their red hats emblazoned with the RF logo in white, their red T shirts with a white cross, and of course their irritating habit of speaking perfectly fluently to each other in seven or eight different languages.

If those Federer fans turned up with a slight feeling of trepidation, it surely went in that opening game - not because of that saved break point, but because their hero got a challenge right. Always less than enamoured by Hawk-Eye, Federer has a bit of a reputation as a serial flop when it comes to making a challenge. If he gets one spot on it's a sure sign that his eye is in.

If it had been a close match, the cries of 'Hop Suisse!' would have started up, and the Saltires and Union Jacks would have been brandished after every big point. But the longer the contest went on, the more it stretched away from Murray, and the more the crowd became subdued. One Saltire was briefly displayed a few rows behind the Royal Box - could it have been the one left behind by Alex Salmond two years ago? One Union Jack on a stick was waved half-heartedly in the seats behind the umpire's chair. And that was about it.

Still, although it was not the closest of matches, it contained some magnificent tennis. Unfortunately for Murray, it was indicative of his plight that the most rousing game of the entire three sets - the tenth game in the second set - did nothing to alter the balance of power.

Serving at 4-5, Murray saved five set points in that game, which was the point at which the crowd became most animated. There were even a few boos for Federer when he went to change his racket at one of the six deuces. He was perfectly entitled to do so - Murray had done the same a couple of points earlier - and after that moment there were no further attempts to paint him as the villain of the piece.

Similarly, it would be a mistake for anyone to treat Murray as the architect of his own downfall. Yes, he has failings, but there is simply no disgrace in losing to the greatest tennis player ever.