Asked about the changes specifically substituting De Bruyne, Scott McTominay and Rasmus Hojlund in the 73rd minute, the coach said: "I tried to bring in fresh players for one-on-one situations because Milan were closing down a lot. I swapped the striker for Lucca and nothing happened... You make substitutions to try and do something good. I think they were the right changes."
Sharing his take on De Bruyne's reaction, the coach said: "I hope he was upset about the result because if he was upset about something else he's got the wrong person."
The Italian coach wasn't pleased with the result but defended the team's overall performance blaming the drop in defensive hold on the lack of players and a congested fixture run.
"We've conceded a few more goals lately, seeing as we did the two goals against Pisa, the two goals today, and the goal against Fiorentina," he said. "Defensiveness has always been our strength, we'll have to be good at improving. Coming here with this performance and playing with this quality against Milan, who are a tough and physically strong team. If they close down, it becomes difficult... It has to give us a good feeling as a team."