The Rossonero won thanks to a brace from Zlatan Ibrahimovic.
Pioli remarked, "I already said yesterday that the result would not be decisive one way or another."
They are top of the table with four wins out of four, conceding only one goal.
“Of course, we're satisfied to have beaten a side that has a lot of quality and caused us many problems, but we held out well and hit back when we had the opportunity.
“It's an important victory, but there's a long road ahead of us and so much we still need to improve.
“I like to think positive and consider myself an optimist, but I also acknowledge there are at least three or four clubs who invested more than we did and are at a more advanced stage. We are ambitious, but largely invested for the future.
“There are seven clubs at a high level in Serie A right now and only four of them will be happy with a Champions League spot at the end of the season.
“If you want to challenge for the Scudetto, you need to raise the quality level of the squad. Even then, it takes a lot of time, there are sides that invested far more and haven't done as well.
“The club has been wise to lay the foundations and build upon them going forward."