Mascherano, used regularly in defence in an ultimately unsuccessful Barcelona season, has been the reported subject of interest from several overseas clubs in recent times.
And Napoli confirmed that they were in the race to sign the 29-year-old, with club president Aurelio De Laurentiis admitting that manager Rafael Benitez liked the player.
De Laurentiis is quoted as telling Gazzetta dello Sport: "Benitez knows Mascherano well.
"We are working on it but it's a difficult negotiation.
"In any case, the player will turn 32 in two years' time."
De Laurentiis added that Napoli would not be selling any of their players as they prepare for another UEFA Champions League campaign.
The Naples-based team will also be looking to improve on their third-placed finish in the Serie A and the president said Benitez is an integral part of their future.
"Right now no one is leaving," he added.
"We have a strong roster and we don't have that many positions to fill.
"We changed 12 players this year and the team has ended the campaign on a high, achieving a club record 104 goals.
"This means that we already have an important foundation. We have planned with Benitez (for) the future and made a list of possible signings."