The centre-back has been linked to a number of clubs but looks set to remain in Naples for now
Koulibaly had been strongly linked with Premier League giants City but Pep Guardiola’s side agreed a deal to sign Benfica centre-back Ruben Dias on Sunday.
Asked about Koulibaly prior to Sunday’s 6-0 demolition of Genoa, Giuntoli told Sky Sport Italia: “The team was completed in January with Stanislav Lobotka and Diego Demme, who can play in a few different roles. With Amir Rrahmani, [Victor] Osimhen and [Andrea] Petagna, we are complete, so will now try to release players who won’t have much time on the pitch.
“I think Koulibaly is staying, we are very happy and so is he. I believe that he is staying.”
Koulibaly helped keep a clean sheet as high-flying Napoli preserved their perfect start to the season against Genoa.
Napoli are yet to concede in two Serie A fixtures this season, while scoring eight goals to top the standings.
Gennaro Gattuso was also quizzed on Koulibaly following Giuntoli’s comments and the Napoli head coach told Sky Sport Italia post-match: “I hope he remains with us, selfishly speaking, because he gives us so much both in technical terms and as a character.
“The world has changed because of the pandemic and I realise all clubs need to balance the books. I hope the call won’t arrive, but I’ll be nervous about it until transfer deadline day.”
The 29-year-old was instrumental as Napoli claimed the Coppa Italia title last season – the club’s first piece of silverware since 2014.
Despite Napoli’s big win on Sunday, Gattuso was quick to stress the scoreline was deceiving.
“This result is very harsh and does not reflect the game,” Gattuso said.
“If Piotr Zielinski hadn’t scored 30 seconds after the restart, it would’ve been a very different match. We have to focus on improving and finding the right balance, because we need balance in order to play this type of football.”