Chelsea took an early lead through Noni Madueke, before City fought back to win 3-1 through goals from Phil Foden, Erling Haaland and Josko Gvardiol.
Maresca said afterwards: "We started the game in exactly the way we prepared. We scored the first one, we could score the second one in three different chances. I think, I am completely sure, because of the mood and because of the moment, scoring the second one, the game would completely change.
"Unfortunately we didn't score the second one. The high pressing; you have to be brave in these kinds of games, knowing that if you have to press higher then you leave their best player - which is Haaland - one-v-one against your defender. But I think we dealt, for most parts of the game, quite well.
"Even the second goal we conceded, we were one-v-one with Trev (Chalobah) but there was all the time to control and manage the moment better.
"For sure, for the way they play, it is not easy to deal because they move and they are masters in the way they play. We tried to do our best and for parts of the game, it worked quite well. We are talking about a different game if we scored the second one because the plan was perfectly working very good; scoring the first one, chances to score the second one.
"In these types of games where the details make the difference, most of the time, the difference is in the box. They are being clinical with the chances they had and unfortunately we missed."
Chelsea goalkeeper Robert Sanchez was at fault for Haaland's goal and Maresca also said: "Robert, for sure, he is completely aware that he has to do better. He was completely aware after the game - he knows perfectly. In this moment, it is like this. The good thing is that he is the first one, knowing and aware that he has to do better.
"We trust Robert for sure. The first one who is completely aware that he is making mistakes in this moment is Robert. For sure we continue to trust Robert. We trust Robert. But now we have one entire week, we will see the reaction and then see for the next game."