There had been a flurry of rumours surrounding both of the players in the last few days. The Partenopei had made a final offer for Witsel, who had putatively accepted the move. They were also believed to enjoy the favour of the Bianconero.
According to La Gazzetta dello Sport, Napoli's offer of €22m plus €3m in bonuses went down well with the Russians, who invited the Italian club to a meeting in which the transfer may be formalised.
Witsel is expected to sign for Maurizio Sarri's team on Thursday. He will earn €3.2m per season, but the club will have his image rights.
Napoli are also believed to have found a deal for Pereyra at €18m, though should any hurdle appear in the negotiations, they will turn their attention to Sunderland's Emanuele Giaccherini.