Hugo Viana, Man City’s incoming sporting director, faces one major task at the Etihad

The Ruben Amorim derby is not the Ruben Amorim derby at all. The Sporting manager is bound for Manchester, but not to take charge of Tuesday’s opponents. But his penultimate game in charge of the Portuguese champions will be the Hugo Viana derby. Manchester City’s next sporting director will come from Sporting, just as Manchester United’s next manager will.

All of which prompted the idea that Amorim would be Pep Guardiola’s successor. Not so, and not merely because Amorim’s destination instead is Manchester United. As City wait to see if Guardiola will want to extend his contract, there may be no frontrunner, because there is no date yet for when there will be a vacancy.

But part of the same rationale was applied by both Manchester clubs. Sporting had not won the Portuguese league for almost two decades. They have now done so twice in four seasons, while improving players, signing well and selling at huge profits. City clearly feel Viana is responsible for a success story; United credit Amorim. For manager and sporting director alike, a move to Manchester comes with a shift in status, to a destination club. City have become excellent sellers under their departing director of football Txiki Begiristain, but from a position at the top of the footballing food chain.

They can testify to Viana’s ability to make money. He signed Pedro Porro from City for €8.5m and sold him to Tottenham for €45m, even if a sell-on clause benefited the Premier League champions. Begiristain has offset City’s considerable spending with an ability to make money in the transfer market, with a profit of over £100m last summer. His successor – Viana will join City in the new year and replace Begiristain next summer – may be given a similar task.

And if Viana’s job at the Etihad Stadium will be framed by the outcome of the Premier League’s case of their century of charges, and could clearly be transformed by potential punishments if they are found guilty, City can project an air of business as usual.

There will be plenty of business for him to attend. If the biggest decision concerns Guardiola’s replacement, the reality is that whoever Viana picks will almost certainly be a downgrade; the questions are by how much and how seamless the transition from one era to another is. The last manager he hired was a spectacular success, in Amorim; though that did not necessarily mean he was ever bound for the Etihad. City were deterred by Amorim’s preference for a back three when their teams, both at senior and junior level, are constructed around Guardiola’s ethos.

But that first team faces change. Viana will be given a rebuilding job. Perhaps City have postponed a couple of major decisions, aware that Begiristain and Guardiola were nearing the end of their tenures.

When the Catalan won his first Premier League title in 2017-18, City had, on average, the fourth youngest team in the division. This season, they have been the fourth oldest (as they were in 2016-17, Guardiola’s first year, when he inherited an ageing team from Manuel Pellegrini), and could have been older again if Kyle Walker and Kevin De Bruyne had been fit more often. Only Everton and West Ham have named an older starting 11 than the side Guardiola fielded for Saturday’s defeat at Bournemouth, which included five thirty-somethings and two 29-year-olds.

City’s squad includes nine players in their thirties – even if one is Scott Carson – plus three at 29 and Rodri, who will be 29 by the time he plays again. There is also a youthful core of Erling Haaland, Phil Foden, Josko Gvardiol, Rico Lewis, Jeremy Doku and Savinho, boasting high levels of quality. But they are outnumbered by the senior citizens and there are areas where City are short of players in the first halves of their careers.

Particularly midfield, where the rebuild may begin. De Bruyne and Ilkay Gundogan are out of contract next summer, when each will be 34, though the German has an option for a further year, followed by Bernardo Silva in 2026. Each, in his own way, feels irreplaceable in the sense of how unique he is: De Bruyne as an extreme creator, Silva with his blend of technique and versatility, Gundogan as an adaptable big-match presence. A further inimitable player may be in decline, in Walker. At 31, Ederson could maintain his standards for years but if there is renewed interest from Saudi Arabia next summer, City might need to plan for life after the goalkeeper.

Meanwhile, the squad has become slimmer. Guardiola is a manager who can face more games with fewer players. He has a reluctance to buy for the sake of buying. But City have not replaced Julian Alvarez, leaving an obvious vacancy for another centre-forward; take the view that Gvardiol took over from Aymeric Laporte and, while Lewis has come through, no one has come in for Oleksandr Zinchenko or Joao Cancelo. As long as the loaned-out Kalvin Phillips feels unsuitable, Rodri is the only specialist defensive midfielder on their books.

The alternative perspective is that City’s youth system and family of clubs means there will be long-term planning. The Argentinian teenager Claudio Echeverri was bought but loaned back to River Plate, but can arrive in January. The American Cavan Sullivan is still younger: perhaps a prodigy, due to join City at 18. The 16-year-old Reigan Heskey scored a hat-trick in Premier League 2 last week. Yet there is a generation gap between them and, say, De Bruyne, which Viana may be charged with filling.

Re-signing the veteran Gundogan made sense in many ways, but it was scarcely succession planning. City have made a fortune by selling but may come to rue letting Cole Palmer leave.

If a lesson of English football history is that dominance is not endless, even when Guardiola’s side have made it seem so, City’s could be ended in the courtroom. Or it may be extended or ended by decisions made in the boardroom, by the choices Viana makes when he recruits players and a manager after starting the job of shaping the new City next summer.