As things stand, Pep Guardiola will not be at the Etihad Stadium past the end of the current campaign. The Catalan was brought in to kickstart an era of dominance both at home and abroad, but as he enters the final year of his contract, only half of that initial objective has been completed.
Guardiola, though, is not the only City icon staring down the barrel of a final shot at European glory with the club.
Like his manager, Sergio Aguero is out of contract at the end of the season, meaning he will be free to talk to other European sides from January on.
Club legends such as Vincent Kompany, David Silva and Yaya Toure have all attempted to win the coveted European prize with City. All have now left disappointed.
Aguero is running out of time if he is not going to follow them by leaving Manchester with a bulging bag of domestic medals but no triumphant Champions League story to tell.
As Goal understands the situation, there has been no movement on a new deal for the Argentina striker as yet, though City have not written off the idea of tying down the ex-Atletico Madrid star to fresh terms.
City chairman, Khaldoon Al Mubarak, insists that both Aguero and Guardiola are free to make their own decisions on their futures and that contract talks with the two will be very "natural".
Aguero, though, has so far remained tight-lipped on his plans, even though he is being linked with a move to Inter, while in the past he has flirted with the idea of returning to boyhood club Independiente in Argentina.
Guardiola, meanwhile, hinted that despite Aguero's legendary status at the club, the forward will need to ensure his performance levels do not drop if he is to earn a new deal.
"We know what he means for us, we know how we appreciate him, but now he has to show like every one of us that we deserve to continue here by playing good and winning games," the former Barcelona boss said of his star striker after Saturday's victory over Arsenal.
“After that, the club and myself, of course, decide, but when he is playing in his level, we don't have any doubts that he is a player to stay until he decides [to go] because he is unique. He is important for us, the fans and for everyone."
Obviously, there is no denying what Aguero has done for City over the past decade.
He is the club’s record goalscorer, the fourth-highest goalscorer in Premier League history and the highest-scoring non-Englishman in the competition's history, as well as the scorer of perhaps the most famous English top-flight goal of the 21st century.
However, as he enters his 10th year at the club, it is only natural that City must ponder the virtually impossible task of finding a replacement – whether that needs to be done next season or the following campaign.
Injuries have interrupted almost every season Aguero has had in Manchester, with his most recent knee problem having kept him out for four months before he made his return this week.
Those fitness issues, combined with the coronavirus-enforced shutdown of football, meant that his successful penalty against Porto in Wednesday's 3-1 victory over the Portuguese champions marked the first time he had found the net for the City first team in 231 days.
Being without a player of Aguero's ability for such a long time would be a blow to any club, but given City's continued reliance on him to lead the line it proved particularly problematic.
For all their qualities, City are not blessed with goalscorers from midfield. Rodri, Ilkay Gundogan and Bernardo Silva were the trio selected against Porto, and between them they contributed a solitary strike (Bernardo vs Brighton in a 5-0 win) while Aguero was missing.
Of course, Kevin De Bruyne – who missed his second straight game through injury – and substitute Phil Foden generally offer more in terms of attacking output, but without Aguero, the goalscoring burden in the early weeks of the season tended to fall on wingers Raheem Sterling and Riyad Mahrez, after Gabriel Jesus also picked up an injury of his own.
Aguero's importance to Guardiola's team was made clear by the fact he was chosen to start a second game in just five days despite such a long spell on the sidelines.
Whether he can go again at West Ham on Saturday lunchtime remains to be seen, but his commitment to the cause, in terms of trying to be on the pitch as much as possible, cannot be questioned.
The 32-year-old worked tirelessly in the gym through June and July in a bid to regain his fitness in time for the culmination of last season's Champions League, and though he came up short, that determination to be there for his team-mates still burns brightly even as he enters the twilight years of his career.
Indeed, his devotion was clear against Porto when, at one particular moment, Aguero chased down an opposition defender to make a challenge rather than leave those duties to someone else.
His penalty saw him become the 16th player in European Cup history to reach 40 goals in the continent's premier club competition, with only two of the other 15 – Ruud van Nistelrooy and Zlatan Ibrahimovic – having failed to lift the famous trophy during the course of their careers.
If Aguero is to avoid joining them on a permanent basis, then this season may prove his final realistic opportunity of winning the Champions League. City have got used to bidding farewell to their legends in recent years, and they would love nothing more than to see Aguero walk away with the biggest prize of the lot.
They know all too well that if any player is capable of providing a heroic final flourish to make their dreams come true, then it is their beloved No.10.