News of Pellegrini's exit and the arrival of the Bayern Munich coach broke on February 1, and was followed by damaging back-to-back defeats to Leicester and Tottenham which derailed their bid for top spot.
City have never been able to regain the initiative and are now 13 points behind the Foxes with five games to go, leaving the Chilean counting the cost of those losses.
He told the Daily Mirror: " Of course for different reasons we lost important games in February, against Leicester and Tottenham - two games which do not allow us to be involved in the title
"I am frustrated because we never expected to lose those games at home against Leicester and Tottenham. But there are a lot of reasons why those things happened. It's not normal in the way we are going to finish the season
"At the start of February there was news about the change of the manager, about players who will not continue here next season, about a lot of things that involved the minds of all the players.
"We had those defeats at home, but now we are stable again and very happy to finish playing the way we have in these last games."
He continued: "It's not easy for the players when you read in newspapers all things that will happen next season - all the players who will go out, all the players that will come in. It's not easy for the players to focus their mind
"But I think the merit of this squad is always that it had a lot of character, personality. We never give up, we continue in the same way, and I hope we will see in the future in the Champions League - I am sure this team, playing in this way, can play in the final."
Source: PA