Kalidou Koulibaly tested positive for coronavirus ahead of Napoli's Coppa Italia semi-final second leg with Atalanta and Serie A meeting with Juventus.
The centre-back returned a positive result on Friday and began self-isolating ahead of Saturday's league game against struggling Genoa.
Napoli are scheduled to face Atalanta for a place in the Coppa Italia final on Wednesday and Juve – who sit two points ahead of them in fourth in Serie A – the following Saturday.
A club statement read: "After the swabs carried out this morning, Kalidou Koulibaly tested positive for COVID-19.
"The player is asymptomatic and will observe a period of self-isolation at home."
Napoli are already without Faouzi Ghoulam for their trip to Genoa after the full-back tested positive for coronavirus.
After taking on Juventus, Napoli travel to Granada for the first leg of their Europa League last-32 tie on February 18.