Mancini acknowledged he had never heard such booing for a new manager from his own supporters.
He said: "I work with another team. But I can say it's very difficult for him and for his team to play well.
"I don't think that Rafa is a magician.
"I don't think he can change everything in a few days.
"Weeks ago, Chelsea were on top and playing well. They have good players. Every manager needs time."
Benitez's fellow former Inter Milan boss added: "To do this job is very difficult. To do it is fantastic. We know everything, but it's a difficult job.
"Also, in England, it's easier than in Italy to do this thing."