The Manchester City manager avoided speaking directly about his Chelsea counterpart but believes his team has improved since a 2-1 defeat to the Blues in October.
The hosts go into the game three points ahead of the Blues and have yet to drop a single point at their own ground in the Premier League so far this season.
Speaking ahead of the match, Jose Mourinho described Manchester City as "lucky," insisting that the club has had "many crucial decisions in their favor" this season, but Pellegrini refuses to be drawn into a war of words with the Chelsea boss and says that he is more concerned with how his own team performs.
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"I do not know what Mourinho has said about us and I have no comment to make about him. I always tell my players that it doesn't matter who we are playing or whether we are home or away."
Chelsea beat Manchester City 2-1 in October at Stamford Bridge, with Fernando Torres capitalizing on a defensive error to score a late winner, but Pellegrini feels that his side is a better team now.
"What is important is that we try our best from the beginning, that we have a winning mentality and that we work well with and without the ball," he added.
"In the last match against Chelsea we made a very important mistake and we lost the game but we have improved since then. All the statistics say we are improving but I have told the players that they must continue to improve.
"We are not invincible, no team is invincible. We are in a very good moment but the difference between a win and a loss is so slight, in every match it is possible you can lose. In December we won nine games and drew one - same in January - but in December we scored 26 and conceded 12, whereas in January we scored 32 and conceded just nine. All the statistics say we are getting better."