The Blues' new ownership invested heavily in the backline in the summer, although the arrivals of Kalidou Koulibaly, Wesley Fofana and Marc Cucurella were to compensate for the losses of Antonio Rudiger, Andreas Christensen and Marcos Alonso.
Now, head coach Graham Potter has added further strength in depth - a priority given Chelsea's tendency to play with a back-three system - and he has turned to 21-year-old Badiashile, who only emerged as a potential transfer target in late December.
But who is the Frenchman, who was handed his Premier League debut against Crystal Palace on January 15, and why have the Blues decided to make an approach in January? GOAL has you covered...