Four players Manchester United need to challenge for the Premier League title, including ex-Chelsea star

3) Centre-back, Mats Hummels

With David de Gea having to put in many stellar performances this season in order to keep out the opposition, Louis van Gaal will need to improve his back line. Sky Sports think that Mats Hummels could be the man to arrive, and the World Cup winner could be a real leader at the heart of the defence.