The Parisian outfit lost 2-1 to Rennes at home in Ligue 1 on Saturday and are now winless in three league matches.
"I am very angry," said the Italian. "I don't think we had a good attitude on the pitch. It's very difficult at the moment because we lost two home games and that's not possible for the team we want to be.
"We're in crisis and I don't have any problems with saying that. We have to get out of this period quickly, and if we have the attitude, character and professionalism, we should do.
"To get out of it, we need to change something, and I will change that something. Everyone has to do more. I am here to make a team and, at the moment, we are not a team."
PSG are currently third in Ligue 1 with 23 points from 13 matches, two points behind leaders Lyon.