City started the campaign in free-scoring style, leaving them open at the back, but since February they have conceded just three goals in the league much to the delight of their manager.
Pellegrini told reporters: "We tried from the beginning of the season to play attractive football and be an offensive and creative team. Maybe at the beginning we conceded too many goals.
"In the second half of the season we improved in defence and are at the moment are a very balanced team."
City are four points behind Premier League leaders Liverpool after 31 games this season, but they do have two games in hand on Brendan Rodgers's side.