Ultras protested after the final whistle with Lazio having won just once in the last nine games.
"We are lacking results at the moment, but we deserved more tonight," Lazio coach Vladimir Petkovic told Sky Sport Italia.
"We made four mistakes at the back and Napoli took advantage of all of them with their ruthlessness. I tip my hat to them, because they didn't let us get away with anything.
"The fan protest? I don't think anything has broken between the team and the fans. We deserved more tonight and have to be more efficient in proving that on the pitch.
"We played on a par with Napoli, but that was not enough. The confrontation with the fans is necessary, whether positive or negative, because we must all be moving in the same direction."
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