It wasn't just Pep Guardiola's first league defeat at Arsenal. A tangible, potential changing-of-the-guard moment. It was the fewest shots one of his sides had produced in a league game for more than a decade.
Down the M23, Roberto De Zerbi's Brighton had just drawn 2-2 with Liverpool. It was not the result they wanted, but one which cemented them as the division's top scorers, an accolade normally the hallmark of any Guardiola side.
Both managers have built the foundations of their philosophies on possession. Right now, De Zerbi's looks the more complete.
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When the two go head to head at the Etihad on Saturday, it could be the away side playing the more expansive football - an unusual turn of events more conceivable when digging into why City's stylistic reboot has stalled.
Guardiola's sides have been unforgivingly ruthless ever since his first day in management at Barcelona 15 years ago, scoring at a rate of almost three goals a game across approaching 900 matches.
There has always been an underlying pragmatism, a desperation for in-game control. But his decision to build a backline around four centre-backs earlier this year, with their title challenge faltering, was far removed from the Guardiola playbook.
After a run to a historic treble within months, it looked like his latest moment of genius.
The underlying creative numbers, while still strong, were not those of Guardiola teams either. Now results are catching up and the solution has now become the new problem.
Shots, opposition-box entries and most crucially goals have dropped off considerably from their previous league-leading totals.
Guardiola is fully aware of the trade-off, but defeat at the Emirates has heightened their cause for concern. An xG of 0.48 was their third-lowest figure under this manager, who watched his side amass four shots for the first time in a league game since April 2010.
The champions have lost all three of the games Rodri has missed through suspension, and he is arguably the Premier League's most important midfielder. No one can move the ball through the lines while offering a defensive shield quite like he can.
But his absence is a symptom rather than the cause given City's longer-term trends.
It would take a brave soul to write them off at this early stage. A wounded Pep is a Pep at his most dangerous, but there is an additional mental consideration this season. What do you buy for the team who has everything?
"I thought there would be a slight treble hangover for City this season. They've achieved utopia, they can't do any more," said Gary Neville after their defeat at the Emirates.
"I think there'll be an element of these City players just having a bit taken out of them. What is their cause this season?"
Things get no easier now. Guardiola has dubbed De Zerbi "one of the most influential managers of the last 20 years", and the Seagulls would leapfrog their hosts with a win on Saturday.
Of course, Guardiola has a history of generosity towards opposition managers shortly before dismantling their best-laid plans.
That could still happen here, in spite of City's dwindling goals. De Zerbi's style is more open than Guardiola's. When it goes wrong, it can go very wrong, like a 6-1 hammering at Aston Villa last month.
But they sit four points off the top, with a brand of football that mixes the keep-ball of Guardiola with much of the verve of vintage Klopp.
They have scored 81 goals in 40 Premier League games since he arrived, and four more than City this season. This is possession with an end product, the hallmark of the best Guardiola teams.
De Zerbi ball has seen more possession than Liverpool, Man Utd or Newcastle this season, racked up more shots from high presses than anyone, as well as topping the scoring charts.
It is a different possession game. Instead of pulling opposition defenders out, De Zerbi's own defence invite a high press before striking through it.
Eventually, opposition sides will find a way to resist, but the results and the goals keep flowing for now. De Zerbi's Brighton have failed to score in just two league games across the last year.
No one expects the Seagulls to finish above Man City this season. That really would be a changing of the guard. But on a comparatively limited budget, with the crux of the midfield which took them to sixth last season gone and now European football to contend with, the 44-year-old's results are performing wonders.
His philosophy marks the league's clearest new tactical thinking since Jurgen Klopp and then Guardiola himself arrived almost a decade ago.
Just as he looked to bring a new spark to old ideas back then, De Zerbi threatens to do exactly the same to Pep and co now.
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