City have conceded 13 goals after 10 league games, their highest total at this stage of a season since 2008-09, when they had let in 16. That tally has prompted questions about their defensive solidity.
City have been pressing high and often in a man-to-man fashion. Anderson has had to cover more space, with his partners in midfield lacking the physicality required to support him. Further concerns have been raised about the skillset of the players behind him.
City were sitting at the top after a flawless start to the season. They are now behind Arsenal and Brighton.
The run has left them six points adrift of Arsenal, who are looking in imperious form as they aim to retain the title.
With possible sanctions hanging over the club, the slump has also raised a wider question: whether recent league form is down to psychological issues, or to tactical problems Maresca needs to address.
The defensive record has changed sharply. In their first seven games of the season, City did not concede any goals because of individual errors. In the past three matches, four mistakes by players have contributed to goals.
This season Maresca has adopted a 3-1-6 shape more permanently, trading a second holding midfielder for an extra attacking midfielder. He and his staff have looked to mould Anderson into more of a sitting midfielder after Rodri's departure in the summer.
Anderson, who has largely impressed, has played to habit, stepping out of a holding midfield position to press or track opposition players and often looking to win the ball back.
It is not problematic in itself to try to coach a player into a key role. City have, though, looked exposed through the middle of the pitch more often in recent games.
When that happens, City can be left with as few as two or three players behind the ball. Opponents then have favourable conditions to counter-attack if they can break the initial press.
After the loss to Forest, Maresca said:"You concede transitions when you lose the ball, and when you don't win duels."For him, the issue is less the shape than losing the ball in the first instance.
A collective efficacy is a squad's belief in its ability to do what it needs to do. Because of success in the past, that belief is often shaken a little by consecutive losses.
Guardiola's solution to some of these issues last season was to ask midfielders to shoulder more of the ball-playing responsibility. With a squad of quality footballers, there is logic in wanting a more front-footed and imposing style. How well those tactics are performed still depends on the skillset of the players asked to carry them out.