Spurs boss Mauricio Pochettino is a big fan of his Argentine compatriot while, across north London, Arsenal have been keeping close tabs on him too.
The 20-year-old has impressed during his 21 league appearances for River so far and he has been tipped as a future star for club and country.
He has already been heavily linked with a move to Europe, with Arsenal and Spurs both keen, but now Napoli are ready to show their hand.
The Stadio San Paolo club are flying this season and are currently just three points behind Serie A leaders Juventus.
They are expected to be busy during the summer’s transfer window and, according to sources in Italy, Mammana is one of their prime targets.