Samu Chukwueze struck the winner as Milan triumphed 1-0 in Chicago today.
Fonseca later said: "I am happy for the courage shown by all the players, I have very good sensations. The result is not the most important thing but winning always causes good things, it makes the players believe in the process. We have a lot to improve but the first three weeks have been positive, we are working hard with an open mind and we can already see that something is happening in the matches they will give confidence to the players.
"(Strahinja) Pavlovic? He has aggression, is a left-footed defender and will bring physicality to the team. The players who are here in the United States have advantages, because they work with us from the beginning. However, Pavlovic will have no difficulty learning our way of playing and defending.
"(Christian) Pulisic and (Yunus) Musah? Christian is fantastic. His quality is incredible, he will be very important this season too. On Yunus, I'm 200% sure that he will be an important player for us, of course he has to learn but he has the right characteristics to play in that position (in front of the defence).
"Liberali plays with courage but we have to think about it, understand what is best for him, whether to go and play where he can have more space or stay here, stay with us for a while and have the chance to play for Milan Futuro. However, all the young people are demonstrating maturity and courage.
"Chukwueze? Last year he didn't play much and when a new coach arrives, everyone wants to show what they can do. I'm really happy for him, he's doing really, really well. I think he will be important in the team and will make the difference."