City, who start the weekend at the top of the EPL, are looking to bounce back from the bitter disappointment of going out of the Champions League after being held to a 1-1 draw by Real Madrid on Wednesday.
But Mancini believes City’s 12-match unbeaten league run this season is under threat after the events at Stamford Bridge this week.
“Usually when one team changes a manager, the game after for the opponents is very difficult,” the Italian told a news conference in Manchester on Friday.
“For us, I think it is more difficult.
Chelsea are one of the best teams in England, in Europe. They have won everything in the last 10 years. Chelsea is a good team with Di Matteo and will be a good team for Benitez.”