On Monday evening, the head coach from the red half of Manchester admitted his biggest fear was his team would sink back to the levels of last season. On Tuesday night, it may have been the other major Manchester manager thinking the same thing.
In their 2-0 defeat to Bayer Leverkusen on Wednesday, City looked like the team who dropped out of the title race in the autumn of last term.
Without the dominating presence of Rodri, City were once again susceptible to opposition fast breaks - where both goals came from, and more should have been scored by the German side. City's attack was unable to match what was created from those defensive deficiencies.
Of course, it was not a normal City team. Erling Haaland did not start the game - when normally he does. And Pep Guardiola rotated all but one of his team against the side ranked third in the Bundesliga table. Such a large number of changes from the City boss is a rarity outside of the Carabao Cup and after the game, even the man himself admitted : "Maybe ten changes was too much."
But this is Guardiola's City - and a manager once famed for his 'Pep roulette' rotation policy. City were once a team who could leave players in their prime such as Kevin De Bruyne, Rodri, John Stones and Ilkay Gundogan on their bench and still deliver with those who took on the mantle.
This City did not look like that. Anyone thinking that City are back and hitting the levels of their four-titles-in-a-row achievement will have rowed back on that viewpoint in recent days following back-to-back defeats.
And it was not as if City put out a team of youngsters against Leverkusen. Nine out of the starting XI will likely go to the World Cup with their countries in the summer - the exceptions being Rico Lewis and Nico Gonzalez, who are part of big national talent pools in their positions.
These were the players City have in reserve if and when injuries strike - in a season where every team seems to be getting injuries.
Many feel City are over-reliant on Haaland - their second-top goalscorer in the league this season is still 'Maxime Esteve own goal' - and Tuesday night's showing adds fuel to that argument.
City's best spell was the 25 minutes after the Norwegian came on - his personal xG tally of 0.62 the highest out of anyone on the pitch despite turning out for just over a quarter of the match.
But right now, City do not seem to have the squad depth needed to maintain consistent levels for matches every three days - a situation they will face in all but one week between now and the middle of January.
Guardiola may have to choose which competition to prioritise between the Premier League and the Champions League, and results in one may make way for the other, like we saw against Leverkusen.
The City boss made his choice this week - with the 10 changes against Leverkusen a clear sign that Saturday's game with Leeds is the priority - with the gap to Premier League leaders Arsenal already at seven points. As he said last week about the Gunners: "If they manage to take some distance in points, it will be difficult to catch up."
But now defeat to Leverkusen means at some point, the Champions League will have to be No 1 in his thoughts - especially if they lose away to Real Madrid in their next European game and lose their grip on a top-eight spot.
And failure to qualify directly for the Champions League last 16 would mean more midweek games in February - and added strain on a squad at a more crucial part of the season.
Meanwhile, the team who sits top of the Premier League and Champions League sits with less angst. And there was a certain irony about City losing at home at this stage of their European competition on Tuesday.
The last time City lost at home in a Champions League group stage or league phase match, it was September 2018. Guardiola was banned from the touchline so, of all people, Mikel Arteta took the City team for that game.
Arteta admitted after that game he was not ready for the hotseat yet, claiming he did not even know how to do a half-time team talk.
But on Wednesday night, Arteta will take his Arsenal team to the challenge of Bayern Munich as one of the Champions League favourites, with a squad already proving able to handle multiple competitions and setbacks.
Phil Foden's back-up was Lewis - with Guardiola reversing that switch at half-time - when Arsenal can alternate Eberechi Eze and Martin Odegaard.
The developing Oscar Bobb is Rayan Cherki's replacement, when Arteta has England's two best right wingers at his disposal in Bukayo Saka and Noni Madueke. Rayan Ait-Nouri was another taken off at the interval, and Arsenal's best-stocked position seems to be left-back. There are plenty more examples too.
Arteta could even make a few changes against Bayern and still keep his team competitive. Arteta appears to have what Pep lacks right now.
