Guardiola suggested the serious renewal will wait until the summer but the red flags have been appearing for weeks in the sudden and shocking decline of a team that has lost the aura of invincibility that left many opponents beaten before kick-off in previous years.
He has had stated City must “survive” this season – whatever qualifies as survival for a club of such rich ambition – but the quest for a record fifth successive Premier League title is surely over as they lie nine points behind leaders Liverpool having played a game more.
Their Champions League aspirations are also in jeopardy after another loss, this time against Juventus in Turin.
City’s squad has been allowed to grow too old together. The insatiable thirst for success seems to have gone, the scales of superiority have fallen away and opponents now sense vulnerability right until the final whistle, as United did here.
The manner in which United were able, and felt able, to snatch this victory drove right to the heart of how City, and Guardiola, are allowing opponents to prey on their downfall.
Guardiola has every reason to cite injuries, most significantly to Rodri and also John Stones as well as others, but this cannot be used an excuse for such a dramatic decline in standards, allied to the appearance of a soft underbelly that is so easily exploited.
And City’s rebuild will not be a quick fix. With every performance, every defeat, the scale of what lies in front of Guardiola becomes more obvious – and daunting.
He will have the finances but it will be done with City’s challengers also strengthening.
Kevin de Bruyne, 34 in June, lasted 68 minutes here before he was substituted. Age and injuries are catching up with one of the greatest players of the Premier League era and he is unlikely to be at City next season.
Kyle Walker, also 34, is being increasingly exposed. His most notable contribution here was an embarrassing collapse to the ground after the mildest head-to-head collision with Rasmus Hojlund.
Ilkay Gundogan, another 34-year-old and a previous pillar of Guardiola’s great successes, no longer has the legs or energy to exert influence. This looks increasingly like a season too far following his return from Barcelona.
Flaws are also being exposed elsewhere, with previously reliable performers failing to hit previous standards.
Phil Foden scored 27 goals and had 12 assists when he was Premier League Player of the Season last term. This year he has just three goals and two assists in 18 appearances in all competitions. He has no goals and just one assist in 11 Premier League games.
Jack Grealish, who came on after 77 minutes against United, has not scored in a year for Manchester City, his last goal coming in a 2-2 draw against Crystal Palace on 16 December last year. He has, in the meantime, scored twice for England.
Erling Haaland is also struggling as City lack creativity and cutting edge. He has three goals in his past 11 Premier League games after scoring 10 in his first five.
And in another indication of City’s impotence, and their reliance on Haaland, defender Gvardiol’s goal against United was his fourth this season, making him their second highest scorer in all competitions behind the Norwegian striker, who has 18.
Goalkeeper Ederson, so reliable for so long, has already been dropped once this season and did not cover himself in glory for United’s winner.
Guardiola, with that freshly signed two-year contract, insists he “wants it” as he treads on this alien territory of failure.
He will be under no illusions about the size of the job in front of him as he placed his head in his hands in anguish after yet another damaging and deeply revealing defeat.
City and Guardiola are in new, unforgiving territory.