Juventus midfielder Claudio Marchisio has stoked up his club's feud with Napoli, saying: "When I am faced with Napoli, something goes off in me."
Marchisio's comments came when Corriere della Sera asked him which individuals or team he dislikes.
A rift between the two clubs has been growing following high-profile episodes in recent months. Napoli refused to collect their runners-up medals after losing a heated Italian Super Cup final to the Bianconeri, and the clubs have since traded insults.
"It's not any particular face but a team, especially after the rough Coppa Italia and Italian Super Cup Finals - Napoli," 26-year-old Marchisio said. "When I am faced with Napoli, something goes off in me."
That prompted an official statement from Napoli in which they claimed they had been insulted and urged both Marchisio and Juventus to clarify the player's comments.
"Marchisio's comments represent a grave insult towards Napoli and all of Italian football," the statement said.
"We are surprised that a player of his stature, who plays at such a prestigious club, would say things like that. We hope it is only a misunderstanding and await clarification from the player and from Juventus."
Juventus later defended Marchisio's comments, saying they were not meant as an insult but to highlight the clubs' rivalry.
"Claudio Marchisio expressed an opinion during an interview," the club's statement said. "This opinion was clearly referring to the healthy sense of competition that has seen Napoli and Juventus take part in fiery and spectacular matches.
"There was no offence: failing to comprehend that means trying to create controversy out of nothing."