Marco Benassi hit a double in the rout.
“I am happy, but there was more to it than the result. Chievo still caused us a lot of problems and at least it means we are capable of suffering under pressure in difficult moments," said Pioli.
“We started the season earlier than usual actually, as we hoped to play the Europa League preliminary rounds, but then Milan won their appeal and were reinstated.
“We had a lot of friendlies and trained well, but there's always the doubt in your mind on how it'll work in a competitive match. This was the big test and Chievo did cause us problems, but we remained a unit and that's what I wanted to see."