I find this all very odd given how long it took Fergie to settle in and how their perseverance paid off for 20 years. Someone at the club it seems has a short memory.
They'll find it difficult to attract the players now, so any incoming manager will have to show great resourcefulness. Only Martinez and Wenger I can think of acquire such attributes.
This thinking has to be based on the logic that anyone given enough time can do a great job as manager, if you can't see the flaw in that logic then I really can't help.
Not all managers are good, just because they gave Fergie time doesn't mean if you pick anyone else on earth and give them several years that they will do the same job Fergie did, that logic is obviously flawed.
Time is not what let Fergie succeed, change is what Fergie used to make the team great. Change that resulted in the most successful era at the club, Moyes showed precisely no such positive change. Much like Wenger, there is no sign of change with Wenger or his teams in 8 years. Players change, identical problems persist, why would it get better. Moyes did nothing positive all year, and came out and claimed on more than one occasion he didn't know what was wrong.
Did Fergie make the team significantly worse in his first season, no, did he fail to make any changes, no, did he publicly claim he didn't know how to make them play better, no.
You can see change in a team before the team is successful. The difference in style and mentality under Rodgers was clear as day last year when they still came 7th. They didn't produce consistently good performances, but the obvious attempts to change the team was clear as day, in wins or losses. That change could have ended up being worse and the team could have been 15th this year, the important part was that there were signs of change and reason to believe it would go the other way. With moyes there has been no game, no tactical change, no performance, no transfer activity, no post/pre game words from the manager, no attitude/mentality changes at Utd this year that look like they can lead to an improved performance next year, none at all. In fact unlike rodgers, or Fergie or Martinez, or dozens of other managers, every sign has been distinctly negative.
There is not a single reason to believe Moyes would improve the team next year and only signs that he would actually make them worse again next year. Firing him was exactly the right decision.
