You cannot compare Fergie and Mourhino, mourhino was just a manager, nothing more, he was very very good and of course his departure affected Chelsea. Sir Alex is more than just a manager. He is a big part of the club, he is ingrained in United culture and is a legend, Mourhino was never Chelsea but Sir Alex IS Manchester United. When Mourhino left then that must have been difficult but if Ferguson left the club would fall apart. He's as much a part of United as Old Trafford and every United fan knows it would be a huge blow if he went, bigger than losing Giggs or Ronaldo or Rooney. When mourhino went it was a simple case of finding a new manager, when Fergie retires it will be an end to an era, the farewell of a legend, Mourhino is not a legend, he was too clinical and arragont to be and he never won a treble or got his team the english record for FA Cup wins, Fergie did.