Napoli president Aurelio de Laurentiis cannot rule out selling their best players this summer.
Azzurri striker Victor Osimhen is being linked with Manchester United, Khvicha Kvaratskhelia is a target for Newcastle United.
After their Champions League win at Eintracht Frankfurt, De Laurentiis said: "I am very good at signing contracts, so when they come to me they are blocked, so keeping them here will not be difficult.
"But never say never.
"Sometimes there are offers you can't refuse, so you never know. In my opinion, we will see them shine for a long time."