Di Canio was unimpressed by their opening day 2-2 draw with Torino on the weekend.
He told Sky Italia: "Milan conceded a lot of goals, especially in transition. Against Torino the same, it’s the same thing we were talking about last year.
“Fonseca has the ambition to make them more aggressive, but due to not physical but mental characteristics, this team, in several players who played yesterday, does not have the aggression. And if they try, they don’t get there.
“(Ruben) Loftus-Cheek cannot play in the two in the middle. Every coach can aspire to do something different because he feels different abilities, but yesterday you had to have two midfielders who do a job like that to free up (Rafael) Leao, instead there was (Yunus) Musah.
“Nobody acts as a filter. (Ismael) Bennacer is not the same as he was 2-3 years ago, because between injuries and other things he is no longer so punctual.
“(Youssouf) Fofana could be a good fit for Milan, he is the real midfielder that Fonseca was waiting for: by sending him forward a lot he gives balance. He can make the difference as a characteristic to send the others
“At San Siro it’s a different story, it’s not the Casino of Monte Carlo. Due to his characteristics, he could be very functional because that type of player is missing in the middle who knows how to dictate the tempo in a clean way and without losing the ball, because in the middle, for example, someone like Loftus-Cheek likes himself, loses the ball and then struggles.”