1) David de Gea / Anders Lindegaard
One game De Gea is no 1 then Lindegaard is no 1 - there was no direction or consistency. Earlier on in the season, De Gea needed backing after some errors, it seemed that this was not given and when United needed to be united from tremendous scrutiny they buckled, dropping De Gea with Lindegaard replacing him. This led to the defence not having a consistent platform in crucial games leading to dropped points, most notably Newcastle away, a game which CIty powered through this weekend.
2) Not buying a center midfielder
It speaks volumes when your starting centre midfielder was a man who retired! The likes of Carrick, Anderson and Cleverley have all failed to fill the void left by Paul Scholes. Sir Alex Ferguson must take some blame towards this as he hadn't prepared efficiently towards Scholes' impending retirement. The market is there for United to purchase a central midfielder, there are dozens of players who would improve the club's options. Lets hope Sir Alex has learnt his lesson and will splash the cash on the likes of Hazard, Modric or another world class midfielder and that United don't turn towards bringing Roy Keane back.
3) Relying too much on Wayne Rooney
Another 25+ goalscoring season for Rooney, however, where would United be without his input? He has carried United in more than enough games. The other players within the team need to step up and contribute more goals. What is the point in keeping Berbatov and never playing him. Surely he should have been moved on last summer in favour of an option Ferguson does rate.
4) Not sticking with Javier Hernandez
Javier Hernandez was last seasons most feared Premier League striker and now he looks like a player with minimal confidence and in desperate need of game time. However, Sir Alex continues to play Danny Welbeck, this is fantastic for England, however, the partnership and understanding that Hernandez and Rooney built last season seems to be wasted. He has had his moments with winners against Everton and Swansea, but these were in the first half of the season and in 2012 he has spent most of his time warming the bench.
5) Reshuffling the back four - and Vidic's injury
Following on from Nemanja Vidic's injury, United never coped with such a big loss. They flattered to at times, but missed him when it really mattered. The likes of Jones and Smalling at at times Evans have failed to step up to the mark. Although Vidic is an excellent player and to fill his shoes is a big ask, the manner in which united have let teams to over dominate them is frightening. The loss to Wigan and 4-4 draw at home to Everton culminated to United pretty much handing the title back to City. Even early on in the season when Vidic was fit, the team was shuffled around far too much, culminating in needlessly dropped points.
Source:http://hereisthecity.com/2012/05/07/five-reasons-why-manchester-united-have-lost-the-title/