David de Gea, Paul Pogba and Romelu Lukaku will all consider their futures if Manchester United fail to qualify for the Champions League. United’s The 4-0 humiliation at Everton on Sunday has left United sixth on 64 points. A Champions League berth is out of United’s hands. De Gea is yet to agree fresh terms, United being forced to trigger a one-year extension on the goalkeeper’s deal to extend it…