It is a hard and pitiless process and it has beaten down many celebrated football men. But who could have anticipated the latest victim? Who could have imagined the taming of Roy Keane?
If you think this a harsh verdict on the situation of a man who may never be surpassed as the Premier League's most influential and inspiring player, you may have missed a recent edition of a UK tabloid, which, for most of the many peaks of his professional life, Keane surely saw as a despicable threat to his ferociously maintained privacy.
Now we see Keane unfurled as the paper's hard-hitting football columnist. The money is no doubt good, but for a man of Keane's accumulated wealth this can hardly be much of a buffer against the reality of his reduced circumstances.
There have, of course, been quite a number of staging posts in Keane's descent from a position of quite implacable belief in his own powers to have a continuing impact on the game to which he brought such a dominating presence as a player for Manchester United and Ireland.
The challenge at Sunderland, which came in the gift of Niall Quinn, a former team-mate he had once mocked as 'Mother Teresa,' went hopelessly wrong.
So did the chance of reincarnation at Ipswich Town, a long drawn-out ordeal which ended, inevitably, with the sack.
Yet if there was a moment which summed up Keane's change of life — and gravitas — more poignantly than his new billing as a UK tabloid's football man, it was surely when he stood, plainly uncomfortably, in the company of his former great adversary Patrick Vieira during the broadcast of a Manchester City game. Vieira played the game amiably enough. Keane looked as if he would have preferred to be on another planet.
Stiff, halting, Keane is not a natural broadcaster. It is as though he has to fight his way through a skein of deep conviction before uttering the most anodyne comment.
Alongside Vieira, his dilemma was nothing short of poignant. You couldn't forget their confrontation in the Highbury tunnel when the war between United and Arsenal was at its zenith. Perhaps we should be more specific. It wasn't so much 'their' confrontation as Keane's. He stepped up to Vieira and said that if he had any issues with a United player, including the relatively diminutive Gary Neville, he should bring them directly to him.
Later, Keane found his most imperious mood. He produced one tackle guaranteed to take away the breath of even Vieira and United won 4-2 going away. Keane left Old Trafford later that year, having exceeded his brief as the spokesman for United's deepest ambitions — at least in the vital opinion of Ferguson.
If it was a shock to Keane's system, he never said. He trailed off to Celtic looking for an authority he would, as it turned out, never quite find again.
He certainly didn't touch on it at the touchline at the City game as he was asked to relax in the company of one of his fiercest rivals. Nor did he find it in his debut offering for a newspaper which prides itself on the stinging quality of its comment.
Guess who he picked to win the title? Manchester United. The solution for Chelsea's embattled manager Andre Villas-Boas was more time, even as Roman Abramovich was planning with his henchmen some disconcerting trips to the training ground. City's manager Robert Mancini, says Keane, had screwed up in the 1-0 defeat at Everton.
Keane, the football analyst, unfortunately doesn't wash, whatever the depth of his playing achievements and knowledge of the game. The meaning of Roy Keane has always had most to do with the force of his passion not his articulacy.
What passion, indeed. It was never expressed more memorably than when he inspired the great United comeback in the Champions League semi-final in 1999, when he took over a United trailing to Juventus in Italy almost as a force of nature.
Now he stands on the periphery of the game and every little nuance of his body language announces that it is far from what he had in mind. That was, it seems safe to assume, to be always at the centre of the action, imposing his will and the certainties he first began to accumulate as a hard-eyed student of the methods of his first great manager Brian Clough. If they seem so remote now, it is maybe inevitable. At the end of last year he fought a public battle with Ferguson, one which seemed to have at its heart the treatment he received when he was banished from the club at 34. Unpromising ground for a man who had lived so often in the triumph of the moment.