Kalidou Koulibaly was the subject of a €100million offer from a Premier League club, according to Napoli president Aurelio De Laurentiis.
Senegal defender Koulibaly starred as Napoli pushed Juventus hard in the Serie A title race last season, although they eventually fell short.
The centre-back, who played all three games at the World Cup for his country, has long been a reported transfer target for Chelsea and Manchester United.
Chelsea appointed former Napoli coach Maurizio Sarri to replace Antonio Conte and have already signed Jorginho from the Partenopei.
De Laurentiis, though, is adamant Koulibaly will not be allowed to leave Napoli.
"It's true, we had a €100m bid from the Premier League for Koulibaly, but we're not negotiating his sale," De Laurentiis told Radio Kiss Kiss.
"He's a very good person and we've never had problems with him."
Napoli are considering Guillermo Ochoa or Francesco Bardi as replacements for goalkeeper Alex Meret, who broke his arm in training six days after joining the club.
"They're two real possibilities on the market," De Laurentiis added. "We want to give Meret the chance to recover without pushing him. He's a young lad and we can't put pressure on him."
Meret, a reported €22m purchase from Udinese, was expected to become Napoli's new number one after Pepe Reina joined Serie A rivals AC Milan.
