Mauro Icardi hit a double to earn the three points.
“We talked a lot about the attitude I want to see not just against a great side like Juve, but also other teams," De Boer told Sky Sport Italia.
“We proved that we are in good shape and this evening started very well with two goals. We used up a lot of energy against Juventus, so it was important to start strong."
Joao Mario was moved to a more advanced role in the absence of suspended Ever Banega.
“We have very important players at Inter, but I think it's even more important than the players understand our philosophy."