The rise and fall of Kyle Walker affirms that old truth that even the most successful players cannot be certain that, when their time comes, they can leave in the circumstances that they may feel their achievements in the game deserve.

At 34, one of the best full-backs of the modern era and a six-time Premier League winner, Walker left for AC Milan today with Manchester City’s season in crisis. Their sometime captain and leader over the last seven-and-a-half years simply slipped away. Pep Guardiola announced before this month’s FA Cup third-round tie against Salford City that Walker had asked for permission to seek a move overseas and so it became clear that he had already played his last game for the club.

Walker heads to a club from the old elite of European football, the likes of whom modern City have done much to dislodge. AC Milan are well set in the Champions League, less so in Serie A, and going there will certainly not make Walker an afterthought in the way that a move to the Saudi Pro League would. Yet even so, it is a departure at a time when City might have expected their senior players to galvanise a squad plunged into unexpected trouble. Walker has gone – his departure a long time in the making.

He has joined AC Milan on loan until the end of the season with an option for the club to buy. He may well return to City in the summer to be sold, and that could be Europe or indeed Saudi. City have launched a major mid-season rebuild and while none of the new arrivals – or putative signings – are right-backs, it requires players to leave. While there is a case for Walker to stay and fight, there is also a school of thought that he is one of those whose form has become the problem. For both sides it is an ending which is less than ideal. Unlike his last contract extension 18 months ago, no one is trying to persuade him to stay.

The pressure of playing for City, of winning every game, under such scrutiny, as the best team in English football, is not to be underestimated. Walker has spoken at length in the past about the toll that exacts. It should also be said that his chaotic private life, principally two children by a mistress who has thrust herself into the spotlight at times, has hardly made that task easier. Quite how that affects his playing career is not clear, but Walker’s private life has not been private for some time, and it has been painful for all involved.

In Saudi Arabia in December 2023, as City completed their sweep of the game’s biggest prizes with the Fifa Club World Cup, Walker talked about the relentless nature of life at the top. The preceding summer he had been persuaded by Guardiola to stay despite offers from Bayern Munich and Juventus – albeit at levels City judged too low. Looking back at Walker’s words 13 months ago it is clear that the task of staying on top was proving exhausting.

He said he had told his team-mates that “nobody is going to roll the red carpet out for us – we have to go and earn the right”. In truth the red carpet was out in Jeddah, where City won the trophy over two games without conceding a goal. But it was probably the last time. City had been through a blip in domestic form that December, insignificant compared to the current crisis. They returned from the Middle East to power their way to a fourth consecutive title.

Yet they came up short in the Champions League and there is something prescient about what Walker said in Saudi as he took stock of City’s season and of his own role. “We’re not killing games off like we used to,” he said then. “We’re always defending on a knife-edge. But us defenders need to deal with that pressure. Sometimes we have to hang on in games and save the day.”

Living on the knife-edge. Dealing with pressure. For seven seasons Walker did that in fine fashion as one of the transformative signings of the Guardiola era. The great Catalan asks his full-backs to live dangerously – a world away from the lives of full-backs of previous eras. A full-back in a Guardiola team will often begin a defensive action out of position. The rest is up to him. Rescuing those situations demands the pace and ability of players like Walker.

Remarkable to think that the £50 million spent upon him in the summer of 2017 was regarded as excessive at the time. One might also say that it was just as valuable for City in reducing the threat of Mauricio Pochettino’s Tottenham team of the time – then the second-best side in the Premier League. City spent the same on Walker’s fellow full-back Benjamin Mendy that summer, a transfer that worked out rather less successfully. That 2017-18 season, City won the Premier League by 19 points. Guardiola had a beautiful idea of how English football might be conquered, although it took players of the ability of Walker to make it work in practice.

Walker’s pace has been key to his success and it is that which often makes the highlights package. Yet a career of his calibre requires more than just being quick. On many occasions for City, and for England, he has had to dispossess the winger coming from the wrong side, which takes delicacy of touch and great physical strength. The king of the non-goalside challenge, so his decline has been a source of fascination too. Not least the losing sprint with Adama Traoré of Fulham earlier this season that went viral when clipped for the official Premier League TikTok account.

That can happen to any great player in his dotage. Just as a young Walker must have made many older wingers think that little bit harder about retirement, there will always eventually be someone swifter and younger to remind you that every player has a finish line. What is less easy to explain is the way in which one of England’s best players, a 93-cap giant, has wrought such damage on his private life to the extent that it came to loom over everything he did.

He has two children with his former mistress Lauryn Goodman, in addition to the four he has with wife Annie Kilner, and he has been the subject of some excruciating interviews. Why he granted one in particular with The Sun this time last year, one can only guess but it was the archetypal tabloid confessional undertaken with all the relish of a proof-of-life video. “Idiot choices and idiot decisions” was his verdict on his own behaviour. “The only person to blame is me,” he said. “I have roles and responsibilities that I’m aware of and I’ve made stupid choices.”

Walker has always claimed, as many in his profession do, that playing football is his release and he is unaffected by his troubles off the pitch. But in Saudi a month before that interview was published he discussed the pain his parents felt at the criticism of their son, and not all of that criticism seemed to encompass his performances on the pitch. By the time Goodman turned up in Germany last summer at the European Championship accompanied by one of her children with Walker, and a Daily Mail reporter, he may have wondered if he could ever escape the bad choices he had made.

Six months at AC Milan is not opting for an easy life, but it seems like it might well be what is required in a complicated life. If he wishes to do so one day, Walker will be able to sit in the television studio with a career the equal of any of the current punditocracy and opine on the next generation. This month it seems he has simply reached his limit and with City in crisis there can be no fond farewell. Time will likely resolve all that. Although for the rest of his problems it may require rather more work.