Carlo Ancelotti was "genuinely surprised" by Napoli's superiority against winners Juventus after both teams were reduced to 10 men, while he labelled Alex Meret's red card "controversial".
Defending champions Juventus moved 16 points clear atop the Serie A standings thanks to Sunday's drama-filled 2-1 victory away to second-placed Napoli.
Napoli goalkeeper Meret was sent off inside 25 minutes as he rushed out to win the ball ahead of Juve superstar Cristiano Ronaldo, who appeared to fall under minimal contact.
Miralem Pjanic scored from the resulting free-kick and Emre Can doubled Juve's lead before half-time, though Napoli were given a boost when the former received a second yellow card for a handball two minutes after the break.
Jose Callejon pulled a goal back for Napoli – who saw Piotr Zielinski hit the post in the first half – in the 61st minute but Lorenzo Insigne was unable to earn a draw with six minutes remaining as his penalty struck the woodwork.
Discussing Meret's dismissal, Napoli head coach Ancelotti told Sky Sport Italia: "It's controversial. He certainly didn't catch him, I can accept it was punished for an attempted tackle. Then you have to take into account where the ball was going, where Allan was.
"Seeing as we have VAR technology, why not view it in totality? It was not a very clear red, as Cristiano might not have been able to get on to that ball anyway. It was going towards the corner flag.
"Meret did not touch him. After that, you have to consider all the other elements. The red certainly changed the game. The only two things we got wrong were the positioning on the wall for Pjanic's free-kick and the corner marking on Emre Can.
"Piotr Zielinski didn't jump in the wall and the ball went over his head. It's destiny, because [striker] Arkadiusz Milik [who was replaced by goalkeeper David Ospina following Meret's red card] was meant to be in the wall…"
Ancelotti added: "I was genuinely surprised by how superior we were to Juve once it went to 10 against 10. It showed how much quality there is in this team, we've got to become more and more convinced of our own capabilities.
"We are having a positive season, changing some tactics and bringing new, younger players in. We must trust our own qualities. We cannot win a game the way Juve did tonight, as we have very different strengths.
"Juventus have great temperament, organisation and individual duels, whereas we have more technique, quality and have to focus on those strengths to win."