Manchester United have had an unfortunate past couple of days after losing out on two of its main transfer targets in defender Nicolas Otamendi and winger Pedro.
However, the Saints insist that the 23-year-old winger is not for sale.
There is plenty of reason for Southampton to hold onto the Senegalese international, as they have already lost two key players.
They sold defender Nathaniel Clyne to Liverpool while star midfielder Morgan Schneiderlin made the move to Old Trafford.
Man United are keen to upgrade their scoring attack though. Mané proved to be a solid scorer for the Saints last season, as he notched 10 goals in 30 Premier League appearances.
The Red Devils still lack a consistent scoring threat outside of striker Wayne Rooney and lost out on Barcelona star Pedro, who joined Chelsea in a £22m deal.
Man United initially made a £15m offer for Mané, but are ready to table a bid in excess of £20m.