The Blues kept alive their title hopes with a convincing win against the league's bottom side, and Pellegrini was pleased at the all-round performance from his players.
"After the first penalty, we played free and could score more goals. I am not only happy because we scored five goals but it was very important the way we defended," BBC Sport quotes him as saying.
"When in attack, it is not always easy not to concede a goal. We have four clean sheets in a row in the Premier League. It is very important to be a very balanced team."
City moved up to third in the table with today's result.