Neven Subotic could leave Dortmund in the January transfer window to be re-united with former manager Jurgen Klopp.
The 26-year old central defender wants first-team football which has become harder to come by at Dortmund since falling behind Mats Hummels, Sokratis Popasthapopoulos, and Sven Bender.
Dejan Lovren continues to look the weak link for Liverpool at the back (along with Simon Mignloet) so a new centre back was bound to be near the top of the list of new manager Jurgen Klopp. Klopp worked with Neven Subotic at Dortmund so the player will know what the manager expects of him.
This a good move for Liverpool, depending on price of course, they strengthen an area where they are weak and get a player who knows the manager and his tactics.