Milan won 6-1 on Tuesday, with Samu Chukwueze (2), Tijjani Reijnders, Rafael Leao, Davide Calabria and Tammy Abraham scoring.
“It was a very good performance, the first half was magnificent and also helped me to rest some players,” Fonseca told Mediaset.
“I have only positive things to say, as we took it very seriously, I am very satisfied with the attitude of the players.
“I always said that I have faith in all my players, that is why they all get to play. I am satisfied today, as some who haven’t played as much this season put in a great performance. They showed me that they are ready and that is what I want to hear.
“I told the players that the most important thing in these fixtures is to avoid relaxation. It was crucial we start strong with intensity, recover the ball quickly, press high, and they did all of that.
“In the past it was a problem caused by the attitude against the smaller teams, but today we showed real progress on that score. I can only be satisfied.
“I am responsible for everything that happens in this side and if we had the wrong attitude before, I will not try to run away from my responsibility for that.”