Ronald Koeman is apparently eager to bring in reinforcements before the close of the window.
The losses of Nathaniel Clyne and Toby Alderweireld this summer have damaged a defence that conceded the second-least goals in the Premier League last season, and manager Ronald Koeman is seeking to strengthen.
Koulibaly’s versatility could prove vital, with the Frenchman able to operate in central defence, holding midfield or right-back.
The giant defender, standing at 6'5, only signed for Napoli last summer - after impressing at Belgian club Genk - yet made just 10 appearances in Serie A last season.
His lack of action hasn’t deterred Southampton however, with TalkSPORT claiming they are close to completing an £8.5 million deal for the 24-year old.
His signing will be a welcome boost after what has been a difficult start to the season.
Southampton struggled to a 2-2 draw on the opening day against Newcastle followed by a comprehensive 3-0 home defeat to Everton on Saturday and there will be concern over whether the Saints can recover from another summer of sales.