Sarri would be a traitor if he joins the Serie A champions, according to Napoli star.
Lorenzo Insigne has warned Maurizio Sarri that joining Juventus would mean "a betrayal" of Napoli.
The Chelsea boss was in charge of Naples for three seasons before he replaced Antonio Conte at Stamford Bridge last summer.
The Italian is now being linked with the vacant Juve manager’s job after Massimiliano Allegri’s departure, and Insigne, who has represented Napoli for his whole career, said the "speculation gives” him “displeasure”.
"It's speculation that gives me displeasure," Insigne told a news conference ahead of Italy's Euro 2020 qualifier against Greece, as onefootball.com quoted.
“He did so much for us players and all the Neapolitan people. He's also a professional, but him choosing Juve would hurt.
"It will be a betrayal for us Neapolitans once it becomes official."
Insigne continued: "I'm sorry to think about him sitting on the Juventus bench.
"He was very important to me for many reasons. I hope he changes his mind. If he went to Juventus he would hurt us but I can't blame him. It’s his decision."