It was a few days after the worst Manchester derby in recent memory that Pep Guardiola decided something had to change.
The goalless draw in December was not the tipping point - that came the following Tuesday night, with a 1-1 stalemate against West Bromwich Albion - but Manchester City attacking play had underwhelmed for months.
Guardiola convened a council of war, bringing together assistants Juanma Lillo and Rodolfo Borrell, director of football Txiki Begiristain and his right-hand man Manel Estiarte.
“We said OK, we have to come back to our first principle and we had to reconstruct the team from that point, what we are as a team, how we had success in the past,” he later revealed.
“We had to come back to our game: move the ball quicker, do more passes, stay in position, run less with the ball, do it together. We don’t have a specific player to win games. We have to do it together.”
City were ninth after that goalless draw at Old Trafford, albeit only six points off the top. Less than three months later, they are 14 points clear, Premier League champions-elect and on an extraordinary 21-game winning streak in all competitions.
What changed specifically? The biggest difference that Guardiola cites is that his players “run less” when they have the ball.
“In football there has to be some pausa,” he told BT Sport this week, using a Spanish term to describe the moment a player will literally pause on the ball, take in their surroundings including the positioning of their team-mates and the opposition, and then make a considered decision on what to do next.
“You have to change the rhythm. If you play a high rhythm you cannot surprise the opponent. This is what we came back to a little bit, to what we have done in previous seasons. Our game was more calm.
“You want rhythm to change in the final third. We came back to those principles and the quality of the players made the rest.”
There were other tweaks too: a gradual shift back to Guardiola’s favoured 4-3-3 system with Rodri as a single midfield pivot; more width, with wingers high up the pitch; a more considered style in possession generally.
Yet while what changed is important, it is just as important that something changed full stop.
Though it is fair to describe Guardiola as an ideologue who sticks by a set of core principles, he is not afraid to tweak, refine or even rip it up and start again when he recognises that something is not right.
Now, ahead of another Manchester derby on Sunday, City prepare to welcome a Manchester United side who find themselves in a similar predicament.
United are simply not scoring. The trip to Crystal Palace was their third successive goalless draw. If they do not break down the Premier League’s best defence this weekend, they will have failed to find the net for four consecutive games for the first time in nearly 30 years.
After Sunday’s 0-0 against Chelsea at Stamford Bridge, much was made of it being the sixth straight game against the so-called ‘top six’ in which Ole Gunnar Solskjaer’s side have not scored.
United’s only goal in these meetings this season remains an early Bruno Fernandes penalty in the 6-1 defeat to Tottenham back in October. And though one theory is that Solskjaer is approaching these games with more caution since that chastening result, that is difficult to justify.
His approach against elite opponents has always been relatively cautious and nothing if not consistent. Generally, United are happy to cede possession, soak up pressure and use the pace of their forward line in combination with Bruno Fernandes’ ambitious passing to exploit space on the counter-attack.
It is a safety-first approach, not that there is necessarily anything wrong with that. It can be an exhilarating game plan when all it comes together - as it did in Paris in October, only a few weeks after the Tottenham defeat.
The 6-1 theory conveniently overlooks that game, as well as the 5-0 against RB Leipzig, the 3-2 FA Cup win over Liverpool and the 2-2 away to Leicester City, who are currently worthier of inclusion in any 'elite' category than Arsenal.
And even during this barren run against the traditional top six, United’s underlying performances have not been significantly better or worse than before.
Prior to the 6-1, United’s average xG difference in top-six Premier League games under Solskjaer was -0.18. Since then, it has only dropped slightly to -0.25.
Whatever the results, Solskjaer has consistently set up with this game plan against elite opposition and it will be a surprise if he attempts to do things differently on Sunday, especially given United’s recent track record away to City.
United travel to the Etihad having won on each of their last two visits employing their usual style to devastating effect, most memorably in last season’s corresponding fixture. It could well be successful for a third time.
The issue, though, is that Solskjaer’s counter-attacking approach to these games leaves everything to chance.
United tend to rely on a handful of opportunities to break in games which are largely played in their own half. They do not seize the initiative, they surrender it. If you do that and then fail to convert the few chances that you produce, you can easily go several games without scoring.
On top of that, City no longer look like a side vulnerable to that approach. They were not vulnerable to it in December, when they limited United to only a handful of poor-quality opportunities.
By the time of their return for the EFL Cup semi-final in January, they had combined that defensive steel with their old attacking verve, scoring two unanswered goals and dominating Solskjaer’s players in every department.
That is all down to Guardiola’s coming away from games like that first derby of the season and asking himself how he and his players could do things differently, how they could do things better.
City subsequently evolved into the best team in the Premier League by a distance and perhaps the best in Europe too.
If United are going to compete at the same level - consistently coming out on top against elite opponents while also beating the likes of Palace, West Bromwich and Sheffield United on a regular basis - their over-reliance on attacking into space will not be enough on its own.
They will have to adapt and refine their game. Like City, they will need to evolve. Whether Solskjaer is ready to take that next step remains to be seen.