2) Mats Hummels (Borussia Dortmund)
One of the best central defenders in the world at the moment, Borussia Dortmund star Mats Hummels is another top class signing both these Premier League giants are looking to make this January as they look to improve at the back. The German World Cup winner could move for as much as £47m, which has seemingly put United as slight favourites to land him.