In football, there often comes a moment when you know things have finally run their course.
In the case of Mick McCarthy, for instance, it came when his chairman marched into the dressing room to announce that he did not intend to pay sheep in Wolves' clothing. Many neutrals have grieved over McCarthy's departure, as one of the few managers whose interviews would leave a polygraph reading as flat as his own vowels. But as he lingered on the touchline after last Sunday's match, like a humiliated general peering through the cannon-smoke for survivors, you could see that he was all played out.
Perhaps the recent indignities of Andre Villas-Boas already represent a point of no return, as well. But the Chelsea coach should comfort himself that there are also occasions when a judgemental consensus can be stripped down and exposed as cliché and idle assumption. Certainly, that was the only conceivable enjoyment available in the television commentary from the San Siro on Wednesday, as one fatuous, insular axiom after another was dismantled by Milan. It was akin to listening to a couple of medieval sailors waiting for their ship to fall off the horizon.
Now Italian football may well remain trapped, to some degree, in a time warp. Its nostalgia for days of glory on the field appears to extend unhealthily into scandal, violence and racism. Arguably, the 2006 World Cup was the very last thing it needed. All the indices, from finance to attendances, are mirrored in the loss of that fourth Champions League slot.
And, or so it is said, there could be no better symbol of this decline and fall than Milan themselves. They have not made the last eight since winning the Champions League in 2007. Before the Arsenal match, Milan were portrayed as the equivalent of a libidinous old fool, insisting on his enduring appeal to Europe's loveliest maidens. Rather as owners and pets are said to grow alike, so Milan were morphing grotesquely into Silvio Berlusconi.
Even the spectacular collapse of this theory on Wednesday was represented in parochial terms, as redemption for Zlatan Ibrahimovich and Robinho – as though they somehow had a point to prove, to our superior football culture. Its real focus, however, should have been a man who shows Villas-Boas just how to channel the self-regard of patron and players alike.
When Massimiliano Allegri arrived at Milan, a rather more extrovert character had just won the treble for Internazionale. Allegri, meanwhile, had little obviously to recommend him to a dressing room that contained (unlike Chelsea's) many international medal winners with club or country. During a 19-year career as a midfielder, he spent just four seasons in the top flight. Even as a manager, he had merely secured Sassuolo a first promotion to Serie B, and then exalted Cagliari to ninth in his first crack at Serie A.
Berlusconi, however, gave him his chance – just as he once did a former shoe salesman, then making his name with Parma in a lower division. It was Arrigo Sacchi who famously remarked: "I never realised that in order to be a jockey, you must first have been a horse." Like Sacchi, Allegri won the Scudetto at the first attempt.
And while his team certainly contained its stars – Milan's first title since 2004, famously, was Ibra's eighth in a row - it still contrived to become greater than the sum of its parts. In the middle of his first season, he signed Mark van Bommel on a free transfer. Van Bommel, 35 next month, seemed only to exacerbate Milan's ageing profile. But a team that had let in 18 goals in 21 matches went on to concede just five in the remaining 15. At the same time, Allegri quietly introduced fresh blood. Nocerino and Emanuelson bossed Arsenal's midfield; on the bench, meanwhile, waited the teenage cockerel, Stephan El Shaarawy, whose performance at Udinese last weekend stifled the first disquiet since Allegri's arrival. (With Ibra suspended, Milan came from behind to become the first team to win at Udinese this season, and so went top of the table.)
It is, plainly, an unanswerable paradox that so unfettered an egotist as Berlusconi should not only hire such a man, but yield to him. The day Allegri arrived, his boss pronounced that Ronaldinho must be accommodated alongside Ibra and Robinho. Allegri, dissatisfied with his work rate, promptly sold him in January.
But the manager who has transformed Kevin-Prince Boateng into one of Europe's most frightening talents only requires commitment as a platform for self-expression. His mentor, at Pescara in the 1990s, was Giovanni Galeone – a charming, innovative coach, devoted to creativity.
Asked how he remembered Allegri, Galeone once said: "Firstly, he was very intelligent. Secondly, I do not believe he has ever set foot in a disco. Thirdly, I have never seen him with a woman who was not beautiful, clever and rich." Allegri, remember, is still only 43 – and only one of several young coaches staunching the financial haemorrhages of the Italian league.
On the pitch, conversely, the Milanello staff continue with their famous conservation schemes. The longevity of players here will not be lost on Robin van Persie, with his history of fragility. Among all the fallout from Wednesday, perhaps nothing was so chilling for Arsenal as a covetous aside from Adriano Galliani, the Milan vice-president. For Van Persie may well recognise this match, and Arsène Wenger's scandalised reaction, as another of those moments that can never be retrieved.