United boss Louis van Gaal is said to be eying a £30m raid for the 23-year-old to boost his side’s toothless attack while Chelsea are also keeping tabs on the Senegalese ace.
But Saints boss Koeman, who has seen a host of star names head for the exit, is determined Mane will not become the latest departure.
He has two-and-a-half years left on his contract and Koeman said: ”We will sell nobody. You can ask every week about Sadio going to United or Chelsea, but we will sell nobody in January.
”The player is developing himself with all the technical staff and the rest of the players.
”The team and the club is growing. We have 17 or 18 international players and they are showing the qualities needed in the Premier League so the big teams are obviously showing interest.