Insigne is not represented by Raiola, but the high-profile agent has been outspoken regarding the potential future movements of some of Serie A's biggest stars.
"Napoli play football appreciated all over the world, that is obvious and everywhere I go, colleagues ask me about them," Raiola told La Domenica Sportiva.
"De Laurentiis should be happy that Sarri is appreciated. Insigne has a contract. We seem to want players to become slaves of either clubs or agents.
"I merely expressed an opinion, that Insigne could happily play for Barcelona, Real Madrid or Manchester United."
Insigne has spent his entire professional career at Napoli, scoring 48 goals in 210 appearances.