According to the Daily Star, the Italian prevented his players from listening to music in the dressing room before and after games, as well as barring all purple clothing and insisting that club meetings took place at odd-numbered times.
A source told the newspaper: "He was unbelievably superstitious and completely lost his temper when a batch of the training bibs and jackets were purple. He said it was an unlucky colour and he didn't want them anywhere near the place. He also said meetings scheduled to take place at an even-numbered time were unlucky, especially on the hour.
"As for the music ban, Mancini said the players wouldn't be able to concentrate if a song was in the background, even though our opponents had their stuff blaring out down the corridor. Once he had his way this place was like a morgue. We have returned to the real world at last.
"The new manager actually talks to the players and staff, which is something that didn't happen for three years under the last guy. Joe Hart can wear his purple jersey without fear of another fall-out, meetings can take place on the hour, and Liam Gallagher can once again be heard ringing out before kickoff."
Pellegrini took over at the club during the summer after Mancini was sacked following defeat in the FA Cup final.