Second-half goals from Patrick Bamford and Kike were enough to see the Championship side progress to the fifth round at the expense of the Premier League champions at the Etihad Stadium.
City???s sluggish performance might have been explained by the fact that their players only returned from Abu Dhabi the day before the game but Pellegrini did not feel that was an excuse.
???I don???t think so,??? said the City coach when asked if that was the reason for the disappointing defeat. ???I don???t agree with you. You can have your opinion but I have a different opinion.
???We had six or seven clear chances to score the goal. In the beginning, I thought we played very well.
???After they scored the goal, we had disorder and they had another counter-attack where they can score more goals. So if people say that???s the reason, I don???t think that???s the reason.???
The result follows another 2-0 home defeat to Arsenal last time out and Pellegrini feels the poor form can partially be explained by the fact that the likes of Sergio Aguero are feeling their way back to full fitness.
???It???s not normal not to have scored in the last two games at home,??? he added. ???I think that???s more to do with football reasons than Abu Dhabi or anything else.
???The problem is that we had to change our style of play because we didn???t have the strikers for around a month.
???After that the strikers are coming back. Of course, they need time to have their best performance and we have to return to the way we normally play. That will take time.???