1. Manchester United have made their point (just)

It was by no means a flawless Manchester United performance. Sir Alex Ferguson still has goalkeeping issues to resolve – Anders Lindegaard's performance must have made him wish Edwin van der Sar could follow Paul Scholes out of retirement – and City, brilliantly, infeasibly, will reflect on those late exchanges when it seemed as though they could pull off the most remarkable comeback. Yet there were other spells when this felt like a United team who had been affronted by the sense of mini-crisis after those defeats against Newcastle United and Blackburn Rovers. They could have brought back Eric Cantona, Bryan Robson and Roy Keane and it would still be difficult to imagine a more devastating first-half performance.

2. And Wayne Rooney made his …

As badge-kissing goes, Rooney's was almost at the point of heavy petting. This was a man who wanted the world to see. It looked pre-meditated and choreographed and in that moment, as Rooney celebrated the twisting header that opened the scoring, there was a clear message that he is not willing to tolerate the perception that his relationship with United is going through one of its counselling stages. A goal celebration does not explain why a professional footballer, paid vast sums, should turn up for training over Christmas looking, to use a generous phrase, worse for wear, and the apology has been noticeably absent. Yet this was the moment Rooney emphatically made it clear that if he was ever intrigued by the possibility of switching from red to blue – City remain convinced he was – those thoughts now belong to the past.

3. Blaming the referee isn't always the answer

For City, the temptation was to blame Chris Foy. They booed him off the pitch at the end. There were cries of "fix" and "cheat" and, at half-time, Roberto Mancini's right-hand man, David Platt, was waiting for him at the entrance of the tunnel. The anger was clear and voluble, and there is no getting away from the fact that Vincent Kompany's red card left them in a state of disrepair. Yet Kompany, as captain, failed his team the moment he launched himself off the ground with both feet. It does not matter what intent he had, or how much of Nani and the ball he got; the simple fact is that a player raising both feet in a sliding tackle is asking for trouble. Foy made mistakes, inevitably, but the bigger ones took place long after Kompany had left the pitch. Aleksandar Kolarov brought down Antonio Valencia for a clear penalty at 3-1 and City could have taken the game to a replay if Phil Jones's handball had been spotted.

4. The great Paul Scholes gamble

He seemed reasonably fit, blowing only a little, considering the last time he had played a professional football match was 225 days ago. He sat deep, for the most part, though there was one moment when he strayed forward a little and was emboldened enough to let fly from 25 yards and, briefly, it seemed as though an unconventional game might have its most eccentric moment. Yet there was one horrible moment, too. It was Scholes who gave away the ball for City's second goal, only four minutes after entering the play, and in that moment it was difficult not to fear he might have been better accepting that the pace of modern-day football is too much for him these days. We shall know more in the coming months, and it is clear that he has given the matter prolonged thought, but it was Scholes himself who was willing to admit last year that, in the vernacular of the game, his legs had gone.

5. The myth about Manchester City's squad size

Perhaps now we understand why Roberto Mancini has been complaining recently that he views the rest of City's winter schedule with a degree of trepidation. They went into this match with only one striker and two fully fit central midfielders. They had two teenagers from their elite-development squad on the bench and Kompany's second red card of the season means they will approach the next four games with only Joleon Lescott, the inexperienced Stefan Savic and Micah Richards, now recognised as a right-back, to play at centre-half. The Premier League leaders produced a brilliant effort of competitive togetherness in the second half but the cold, harsh reality is that are starting to look a little thin round the edges and with the introduction of Uefa's financial fair-play regulations, there is no guarantee they can just chuck money at the problem like before.