City currently find themselves in seventh, four points behind leaders Chelsea having drawn with Liverpool and Arsenal so far this season.
The Premier League champions are now without a win in four games having lost to Aston Villa in the Capital One Cup on Tuesday and Maicon is adamant that the club needs to improve.
"It is difficult to say why it is happening because I only just arrived at the club," said Maicon.
"The beginning of the season is difficult and a lot of clubs are conceding goals.
"But I know that Roberto [Mancini] is very focused on it. He wants to improve and we have to improve quickly because we can't afford to have any more distance between us and the teams at the top of the league."
City travel to Fulham on Saturday.