Was this the day the title was won, after a moment that saw Manchester City lose their composure, and thereby the game?

An impressively full-blooded Manchester United were still full value for a 2-1 derby victory that now leaves the champions 14 points behind Liverpool, a gap that no one in the history of English football has ever recovered from.

Almost every moment of this match certainly felt freighted with greater significance, for reasons even beyond the title.

Liverpool’s earlier 3-0 win over Bournemouth had after all framed the afternoon, but it was Ole Gunnar Solskjaer’s future that had framed much of the week. It now won’t influence any chat about the sack, or Mauricio Pochettino, for a long while. His team responded perfectly. They claimed yet another fine win over a big-six side – and the second of the week – with this even more impressive than the midweek victory over Tottenham Hotspur.

That was because United were so admirably all in. If there remain fair questions over whether Solskjaer’s tactics are best suited to the best sides – with fixtures over the big six remarkably forming 50 per cent of their mere six league wins – there should now be more pointed questions about one specific element of Pep Guardiola’s management that has left City losing a remarkable five games before Christmas.

Ratings: City vs United Show all 25 1 /25 Ratings: City vs United Ratings: City vs United Ratings: City vs United MANCHESTER, ENGLAND - DECEMBER 07: Players of Manchester City and Manchester United wait in the tunnel prior to the Premier League match between Manchester City and Manchester United at Etihad Stadium on December 07, 2019 in Manchester, United Kingdom. (Photo by Victoria Haydn/Manchester City FC via Getty Images) Victoria Haydn Manchester City FC via Getty Ima Ratings: City vs United Manchester City Manchester City's Spanish midfielder Rodri (2L) and Manchester City's Brazilian midfielder Fernandinho (2R) remonstrate with referee Anthony Taylor (C) as Manchester City's Belgian midfielder Kevin De Bruyne (R) reacts over a penalty appeal during the English Premier League football match between Manchester City and Manchester United at the Etihad Stadium in Manchester, north west England, on December 7, 2019. (Photo by Oli SCARFF / AFP) / RESTRICTED TO EDITORIAL USE. 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Please contact your account representative for further details. PHIL NOBLE REUTERS Ratings: City vs United Kyle Walker - 5 MANCHESTER, ENGLAND - DECEMBER 07: Kyle Walker of Manchester City crosses the ball during the Premier League match between Manchester City and Manchester United at Etihad Stadium on December 07, 2019 in Manchester, United Kingdom. (Photo by Chloe Knott - Danehouse/Getty Images) Chloe Knott - Danehouse Getty Images Ratings: City vs United John Stones - 5 MANCHESTER, ENGLAND - DECEMBER 07: John Stones of Manchester City looks dejected following Manchester United's second goal during the Premier League match between Manchester City and Manchester United at Etihad Stadium on December 07, 2019 in Manchester, United Kingdom. (Photo by Michael Regan/Getty Images) Michael Regan Getty Images Ratings: City vs United Fernandinho - 6 Manchester City's Fernandinho, left, discusses with referee Anthony Taylor during the English Premier League soccer match between Manchester City and Manchester United at Etihad stadium in Manchester, England, Saturday, Dec. 7, 2019. (AP Photo/Rui Vieira) Rui Vieira AP Ratings: City vs United Angelino - 4 MANCHESTER, ENGLAND - DECEMBER 07: Scott Mctominay of Manchester United and Angelino of Manchester City in action during the Premier League match between Manchester City and Manchester United at Etihad Stadium on December 07, 2019 in Manchester, United Kingdom. (Photo by Chloe Knott - Danehouse/Getty Images) Chloe Knott - Danehouse Getty Images Ratings: City vs United Kevin De Bruyne - 6 Manchester City's Belgian midfielder Kevin De Bruyne heads the ball during the English Premier League football match between Manchester City and Manchester United at the Etihad Stadium in Manchester, north west England, on December 7, 2019. (Photo by Oli SCARFF / AFP) / RESTRICTED TO EDITORIAL USE. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 120 images. An additional 40 images may be used in extra time. No video emulation. Social media in-match use limited to 120 images. An additional 40 images may be used in extra time. 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Please contact your account representative for further details. PHIL NOBLE REUTERS Ratings: City vs United Bernardo Silva - 5 epa08052508 Manchester City's Bernardo Silva reacts during the English Premier League soccer match between Manchester United and Manchester City held at the Etihad Stadium, Manchester, Britain 07 December 2019. EPA/PETER POWELL EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or 'live' services. Online in-match use limited to 120 images, no video emulation. No use in betting, games or single club/league/player publications PETER POWELL EPA Ratings: City vs United Gabriel Jesus - 4 MANCHESTER, ENGLAND - DECEMBER 07: Gabriel Jesus of Manchester City controls the ball during the Premier League match between Manchester City and Manchester United at Etihad Stadium on December 07, 2019 in Manchester, United Kingdom. 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What was really relevant to how the game panned out was just how spooked they were by that correct penalty decision.

This was a clear case of the first goal deciding a match, but not because it put United ahead. It was because City were so put out.

The champions hadn’t exactly been brilliant before then, but it was at least an end-to-end match wildly swinging from box to box. The game decisively swung one way for a key 15 minutes after Bernardo Silva clumsily tripped Marcus Rashford – in what, it must be said, was as clear a penalty as you’ll see. All of the action was around Ederson’s goal, and it could really have been all done then. United might well have been 3-0 or 4-0 up. They were that good, that focused. City, however, were that bad.

What summed it up was the simplicity of beating their backline for the second goal. Dan James and Martial were able to almost walk through them, against non-existent challenges, before the French forward enjoyed the time to pick his spot on the inside of the post.

Rashford put United in the lead with an early VAR-awarded penalty (Getty)

The City players had displayed much more intensity and aggression in remonstrating with referee Anthony Taylor for the earlier Rashford penalty, but that alone might be the cause of the contrast.

This was far from the first time that this City – or, in truth, a Guardiola team – suffered a temporary melt-down after a decision they felt aggrieved by. It has happened against Tottenham Hotspur, against Liverpool, and for Guardiola himself against Atletico Madrid with Bayern Munich and against Chelsea with Barcelona.

It’s difficult not to think this is one area where Guardiola’s famous intensity goes from an extreme positive to a big negative, not to mention the damage done by always going on about decisions in the media. It is like his team start to reflect and radiate his touchline histrionics and stop doing things in the focused way they’re usually supreme at. That was probably all the more pronounced here because the sense of injustice was itself intensified by the knowledge this was the title on the line. It was that big.

They were in that much disarray. Rodri did not seem to know where to go. Gabriel Jesus was fluffing easy chances. David Silva was hesitantly patting at balls he should have been drilling. The defence was in a constant stage of agitation.

Rashford was the opposite, so calm in taking that key penalty.

The doubts and hesitation he seemed to suffer with spot-kicks earlier in the season appear to have been dealt with, as he has clearly developed a routine. Gaizka Mendieta-like, Rashford waited for Ederson to commit before rolling it into the corner.

Martial doubled the advanatage before half-time (Getty) (Manchester United via Getty Imag)

City, to give them their due, did recover from that spell – at least mentally.

By half-time, they were back moving as a properly functioning team, and back pressing United in the way that causes such problems.

The problem for City, however, was that United remained just as intensely focused.

They knew the significance of a win here for their manager, and the club at this juncture. Every tackle reflected that, illustrating an intensity of application that only comes with these biggest of fixtures.

There was one challenge by Aaron Wan-Bissaka on Raheem Sterling that had such force that it also had a lot of risk about it – but he was rewarded for that extra effort. He came away with the ball. Fred meanwhile always seemed to be winning it. United just had that determination to always get anything on the ball, as when Victor Lindelof just about touched away a Kevin De Bruyne shot. It was enough in the moment.

The lead was enough on the day. Nicolas Otamendi scored late on but the damage had been done, in that key spell that has also fatally damaged City’s title challenges.

United have done their biggest rivals the biggest favour in beating their closest rivals, but this wasn’t really about any of that.