Centre-back Guehi’s £20m arrival from Crystal Palace in January was considered a bargain.
But it was his loose pass at Everton late last season which cost City dearly in the title race, drawing that game and losing the impetus to eventual champions Arsenal.
This season has been a struggle for the England defender, culpable for both goals scored by Ipswich last weekend and being picked off by John McGinn deep in his own half for Villa’s first goal.
Later in the half, he hauled down Jackson on the edge of the box before being shown a yellow card, and was put out of his misery by being taken off at half-time.
City sources had said they were targeting signing a right-back in the summer before pivoting elsewhere, saying Abdukodir Khusanov can provide back-up should Matheus Nunes not be available.
Khusanov started out wide but struggled before being moved inside in place of Guehi, while Rico Lewis was brought to fill the gap, with Maresca acknowledging afterwards he needs to “find that balance” in defence.
Villa supporters provided constant reminders to the travelling fans of their side being “cheats”, and the vitriol faced following the guilty verdict of the financial charges may be beginning to weigh on the players’ minds.
Asked by BBC Sport if Guehi’s form is a worry, Maresca said: “No, I’m not worried about Marc at all.
“I know he is playing every minute since the season started with us and the national team, so it’s not easy but the change was also because he was on a yellow card.
“The way we want to be aggressive sometimes, to have one yellow card can be dangerous but I am not worried at all.”
Maresca, though, should be concerned by coming up against Fabian Hurzeler’s free-scoring Brighton twice next week – in the Carabao Cup on Wednesday, and Premier League on Saturday.
The Italian needs to fix the defensive leaks before they become something more serious.
