In spite of the heavy summer recruitment, the Azzurri are expected to sign few more high-profile players in January and the Belgian is one of the first names on their hit-list.
Napoli are prepared to offer over €20 million for the highly rated footballer, while they could also include striker Eduardo Vargas in the deal.
The player, who is currently on loan at Gremio, is wanted by Zenit and he could be used as a bargaining chip.
Zenit seem ready to cash in on Witsel for some €30 million even if they paid around €40 million for his services just a year ago.
The 24-year-old has since made 27 Russian Premier League appearances for the club, scoring 4 goals, but it appears that he is looking to return to the biggest stage at the earliest opportunity.