"At the start of February, there was news about a change of the manager, about players who will not continue here next season, about a lot of things involved in the minds of all the players," Pellegrini told British media.
"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.
"In February we were involved in all the competitions, in the Champions League, we won the Capital One (League) Cup, we were forced to leave the FA Cup, and we were three points behind the leaders."
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Third-placed City, 13 points behind leaders Leicester City, have since picked up from the dip and are unbeaten in their last five games, winning 3-0 at Chelsea on Saturday.
They have also progressed to the Champions League semi-finals for the first time and will take on Real Madrid.
Pellegrini put the change in form down to the players' increased concentration levels ahead of their trip to relegation-threatened Newcastle United on Tuesday.
"We must try to finish now playing this way, trying to be as near as possible at the top of the table, trying to reach the final of the Champions League and we will finish a good season if we win two titles," the Chilean said.
(Reporting by Shravanth Vijayakumar in Bengaluru. Editing by Patrick Johnston)
