Chelsea are looking to bolster their defense after losing Levi Colwill to injury. The Blues are monitoring the development of the young Frenchman, who has scored once in 22 appearances this season.
Interest in Coulibaly extends beyond Stamford Bridge, with Real Madrid, Manchester United, Newcastle, PSG, and Napoli also scouting the player. Werder Bremen is reportedly holding out for a fee between €40m and €50m.