It is a truth that can be verified by statistics: most teenage boys end up being men. Some take their time about it - a decade and more is not unprecedented - but most of them get there in the end, even though there were times when all around them despaired.

One of the hard facts of sport is that you don’t have time for that. You simply cannot hang about. Athletes who have a languid, take-it-as-it-comes approach to maturity are seldom to be numbered among the achievers. If a male is to become a serious winner in sport, he has to reach manhood at the earliest possible opportunity.

Andy Murray has shown signs of having done exactly this over the past few months. He has abandoned the persona of the gap-year kid with a grudge against the world, and has instead, match by match, turned himself into a sportsman of substance. It is not the case that he has come of age over the past couple of days. He has merely supplied the proof that he has already done so.

His journey to the semi-finals of the US Open was not always smooth, but it was characterised throughout by Murray’s transparent belief that he had a perfect right to be where he was and getting the results he was getting. He acted like a grown-up who had long been one of the world’s top four tennis players: not at all like a kid forcing his way into to world of the grown-ups. He behaved as if his right to be there had already been established. That was the triumph: that was the sporting maturity.

Yesterday he reached the final by beating the world No 1 with a display of scintillating tennis, outrageous stubbornness and the finest display of big-match temperament we have seen from a British player since – although most of us must take this on trust – Fred Perry in 1936. Murray didn’t look like a player who could nick the odd result. He looked like a future world No 1.

He had a day of dreams on Saturday, a day on which Rafael Nadal was slightly off his game, while Murray was as deep into the zone as ever a tennis player could be. He ran up a two-set lead, but a more severe test awaited him yesterday: a resurgent Nadal, a crowd backing his opponent, and he a man noted for his ability to come back from two sets down. It was, in short, Rafa’s stage. Murray found himself an intruder at his own party.

But he was able to ignore all of that. He lost the third set, from being a break down overnight, and a rampaging Nadal was on the point of bullying him out of his first service game in the fourth. But Murray simply wasn’t having it. The Scot responded to the sight of Nadal playing his best tennis by playing his own best tennis. And that is the sort of thing that champions do.

But champions also take the next step. Often it’s the smallest step – almost always it’s the hardest. We had the majestic sight of the two of them going toe-to-toe at the beginning of the fourth set: Murray fighting Nadal’s power with his own power, Murray countering Nadal’s intensity with intensity of his own. Murray piled into Nadal’s service game and took him to the edge seven times. Murray was magnificent, Nadal saved all seven. Even more magnificent.

That’s when Murray betrayed the first sign of callowness of the entire fortnight, losing his next service game to love. And we all knew what would happen next: the great intimidator would intimidate, the Brit would instantly lose his pluck. And nothing of the kind took place. That’s when Murray strode away and won. It was unforgettable stuff.

What we saw yesterday was a mature athlete, with highly honed skills and the nerve to use them to destroy the best player in the world. Murray has arrived and he’s going to do something remarkable. Maybe even today.