Pellegrini not tough enough to maintain City's new order
For Manchester City and their embattled manager Manuel Pellegrini - and such discredited superstars as Yaya Toure and captain Vincent Kompany - the challenge at Old Trafford on Sunday is not so much Louis van Gaal's laboriously renovated United.
It is the cold hand of football history. For the first time since November 2013, United have the edge in the city's old visceral battle for supremacy and if the margin is fine - just one point - the meaning of it could hardly be more daunting for the flagging champions.
They thought, with all their talent and underpinning of wealth, that they had put a little clear blue water between themselves and their old masters.
But then that's the challenge of history. If you don't understand what happened yesterday, how are you going to get some firm hold on the future?
City and their richly-rewarded players have committed the crime that was sought out and ruthlessly punished by the great Old Trafford empire-builders Matt Busby and his trophy-hoarding heir Alex Ferguson.
Yes, the world of football has changed in so many ways since Busby first laid down the foundations of a winning tradition.
Corporate values have supplanted the old sweet simplicity of a strong manager and largely submissive, modestly paid players. Yet some things never change, and one of them is the imperative of powerful leadership.
Busby was a silky diplomat but he was also a steely, demanding leader who sniffed out signs of complacency. Once he marched from his office on to the training field and dressed down a player he believed to be idling. "That's not Manchester United," he declared, and nor was the culprit in a matter of weeks.
Ferguson, of course, was fair-minded in his use of the hair-dryer - and the pink slip of dismissal. He applied it to everybody and not least brutally to his biggest stars, including Roy Keane, David Beckham, Ruud van Nistelrooy and Jaap Stam.
Now, after the strange and unsettling hiatus presided over by David Moyes, it seems that United are back in the old mould - one which insists that no-one is beyond the hard edge of a powerful manager.
It is in this area of football club culture that the City crisis has to be held up to the harshest light - and in it the amiable, civilised Pellegrini is inviting what is looking increasingly like terminal doubt.
Some of it was expressed this week by Joe Corrigan, who grew up to be an England goalkeeper in the fierce regime of super coach Malcolm Allison and his often jocular but fiercely competitive manager Joe Mercer back in the glory years of the late '60s.
Corrigan said: "The manager can tell the players what he wants on the pitch but it's the players who go out and it's their pride on the line. Not all the (City) players but some of them don't seem to have the passion to go out to win."
No prizes here for guessing who the big man had in mind. Most dispiriting of all for City loyalists is the sense that Toure, who not so long ago was one of the glories of the Premier League, has lost much of his old appetite for the grandstand performance.
His shortfall in the old dominance has been critical in the team's failure to make a champion's defence of a title - and also dismaying has been the form of another former City banker, Kompany.
The Belgium defender was recently left on the bench - a development which doesn't seem to have cured him of a severe case of hubris. After the shocking defeat at Crystal Palace - City's third in five games - the captain declared that Old Trafford was the perfect place for the team to gather back some of its old strength. A good place, perhaps, but surely laggardly timing as Chelsea sit nine points clear of the champions with a game in hand.
The charge against Pellegrini is forming around the idea that he simply isn't tough enough to provoke more consistent commitment from his expensive charges.
Sergio Aguero remains a world-class operator of some passion, but injuries and frustration have tugged at his effect. David Silva is too often isolated in his brilliant instincts. Overwhelmingly, there is the impression of a team which needs re-seeding, refreshing and, perhaps literally, re-booting.
Certainly the contrast between Pellegrini's mild manner and the aggressive ego of an Gaal could hardly be more extreme.
Van Gaal's former player at Bayern Munich, Franck Ribery, was plainly in no mood to be complimentary with some reflections on his old boss but what he said may have carried us to the heart of the Dutch dictator's work at Old Trafford.
Ribery said: "We had problems with him on a human basis. When he started no-one knew what was going to happen. His idea was that he didn't care about names at all, you don't need stars, he said, everyone has to prove themselves again.
"The first contact with him was already poisonous. As a professional you lose your trust.
"He does great things on the pitch but the coach Van Gaal was a bad man. Our relationship was already crushed."
Remarkably enough, Bayern still managed to carry off the Bundesliga title and the German Cup and when Van Gaal left to take over the Dutch national team it was not because of his failed leadership but his habit of squaring up to the old player elite who still wielded huge influence.
Van Gaal may not be the most engaging dinner guest but his tendency to get results, right up to last summer's over-achievement with the Netherlands in the World Cup, is embedded in a winning career.
One of his heroes in Brazil, Dirk Kuyt - a notable trier in any situation - was much more generous than Ribery.
He said: "Under Van Gaal no-one is in doubt about what is expected of them. He makes that clear and if you put in the effort, if you play as well as he knows you can, you don't have any problem."
Old United players like Gary Neville and Paul Scholes have from time to time offered some tart analysis of Van Gaal's team development, but no-one can argue that he hasn't delivered on the most basic of his promises - the one proved quite beyond the powers of the fallen Moyes.
He has led United back towards the Champions League with growing authority, and if his football is still to glitter in the old-fashioned way, he has plainly installed the value of heightened commitment.
Celebrity, and past achievement, wins no favour in the United dressing-room. It means that on Sunday they are more than a threat to Pellegrini's tenure.
They are a reproach that carries, no less, the force of old but still highly relevant football history.