If this really is the City breakthrough, and certainly there is some evidence to go along with, they need not worry too much about the large irony that is at its heart.
This is that at a time so discouraging their manager, Roberto Mancini, cast them as a sumptuously heeled version of Birmingham City, it was the inadequacies of their previously dominant rivals that so conspicuously helped them on their way.
They took what was on offer with a smash-and-grab certainty that would have pleased their old marauders Mike Summerbee and Francis Lee and it was not their fault that at times Manchester United might have been contributing to a charity store.
City, naturally, could hardly care less because every successful experiment is in need of a catalyst and it just happened that only someone wearing the tightest wrapped blindfold could have missed the one that changed everything here.
It came when Michael Carrick betrayed his most promising run of form in three years and allowed Yaya Touré, the best player on the field by some distance, a run on goal that was unanswerable in both its power and its conviction and claimed, furthermore, the huge scalp of a completely overwhelmed Nemanja Vidic.
United were further debilitated when Paul Scholes produced arguably the ugliest moment of his twilight years.
When Scholes has been good he has touched the sublime; when he is bad, the opposite is precisely true. His tackle on Pablo Zabaleta was a despicable combination of physical crudity and red-mist malice and, maybe, fatigue that must make his admirers worry about quite how many opportunities for redemption he has left.
However, this in the end was about City – and in the moment of exhilaration that came with the knowledge that they were on course for their first trophy in 35 years, the possibility that they may have indeed moved beyond the impasse so long denied by some of their most impassioned, if not irrational zealots. This is the one that has, for some of us insanely, limited their ambition to play football more appropriate to a club of their resources.
The fact is that for a spell after Touré's strike, City looked entirely the way they should have done for some time now. They looked like a team filled with the belief that beating, in this case, one of the two most consistently competitive clubs in the history of English football was not an ambition but a right.
Certainly, it is reasonable to believe that the exhilaration which came here with the final whistle represented a major charge of confidence that should serve them well in their hand-to-hand duel with a Spurs cuffed down to earth by Real Madrid.
Maybe Mancini, no longer the Italian pragmatist but a jigging, joyous embracer of every piece of available flesh, will be more inclined to trust performers of the quality of Touré and David Silva and Adam Johnson; be at least a little more susceptible to the idea that something like Champions League qualification is an ambition best placed in the heart and confidence of his players than projections based on a slide rule.
This might just be the gift of a win that was barely advertised in the first 20 minutes or so, when Dimitar Berbatov twice reminded us that he rarely brings the finest cutting edge of some wonderfully fluent skill to the most important occasions.
His woeful failure to pull the trigger made you wonder what Javier Hernandez was doing on the bench, a question that could only be reinforced by the fact that the young Mexican later came so close to exploiting a far more difficult chance than either of those served up so perfectly wrapped to the Bulgarian.
Again, though, this is no concern of City. They survived and they prospered with football of authentic quality, and especially when Silva and Touré were on the ball.
Mario Ballotelli was asked to cover a lot of ground but, apart from the odd flash of skill, again didn't do much more than suggest he would have been a disruptive presence at the Last Supper. However, the reaction of Anderson and Rio Ferdinand to his post-game gesturing was less a rebuke to him than evidence of deep frustration at the failures of their own team.
Gareth Barry, after being deeply compromised by the ease with which United set up Berbatov, emerged from his early ordeal with some composure and Vincent Kompany and Joleon Lescott soon enough were putting out the fires that had earlier crackled around them.
It left us with some fairly straightforward conclusions.
The follies of Carrick and Scholes certainly arrested the sense that United's season had moved, after all the uncertainties in the early going, on to another plateau of confidence – though the impact of the absence of Wayne Rooney in his current form could hardly be overstated – and for City there was plainly an injection of self-belief.
Touré's engulfing of Vidic and his shot beneath Edwin van der Sar should serve as the motif of resurgence or, better still, a statement of quite what can happen when a team of genuine ability comes, for one reason or another, off the leash.
For a little while City were not only punching their weight but doing it with an exuberant hunger for the ball.
Silva, particularly, became a brilliant expression of creative instincts. It should mean that City have indeed achieved a watershed, a point in their existence where the idea of going to places like the Emirates, Old Trafford and Stamford Bridge with no greater ambition than picking up a few scraps is consigned to the rubbish pile of bad ideas.
This, of course, should not embrace the kind of hubris that gripped the great Malcolm Allison the last time City had reason to entertain the highest hopes for their future.
After winning the title at Newcastle, Big Mal declared, "Next stop, Mars." It was in fact Istanbul and elimination in the first round of the European Cup. To be fair to Mancini, and despite the promise exhibited here, he is not likely to make the same mistake.