2006 should not be counted as disappointing in my opinion. We went out of the CL in December. After the 3-4 loss to Blackburn rovers, we went on a pretty great run with only 1 draw and no losses till the Chelsea game and won the League Cup. 2006 was when we brought Vidic and Evra who formed our best defensive group with Ferdinand and Neville, and Brown whenever Neville was absent. Underachievement is what showed that we have a more capable team who can and might do better. Same situation we are in now, where we know that this team can play much better and show more of what they are made of. There was no doubt about Fergie ever quitting and no one thought that he should during those times. Whereas, even with a promising team of talent and pace, many think that the team might be shackled with Jose's tactics and might improve if he give some leeway to be more attacking or leaves United.