Very rare, but:
- Having no idea what to do with Veron.
So the saying goes that the league was too fast for Veron. The reality is we bought him and didn't give him the midfield, instead keeping Keane as the main man with Veron a very peripheral figure basically cheerleading and looking quite lost as to what he should be doing. Veron was top 3 in the world at what he did at that time, but we never allowed him to play like he did in Italy or for his country. Keane of course, was also top 3 in the world at what he did, plus he was the captain, plus it was his team, plus he was entering his peak so.... unlucky Seba. We bought him to become consummate performers in the CL utilising a denser, more cultured midfield, but it never worked out he could have if Veron didn't have to defer to Keane and relinquish most of what made him so good.
- Buying Berbatov.
We had the best frontline in the world at that time, and they were growing and developing as a unit. Tevez was not quite himself, but the signs were there that the 3 of them had gears to go up and it should have been our time to dominate the CL. In comes Berbatov, and our game changed, our flow suffered, Tevez's nose got knocked out of joint and Berbatov's style did not mesh with the wild, vibrance, aggression and unpredictability of the other attackers. It didn't work out as it was envisaged to and made us a lot easier to play against compared to the dynamic, cross-positional play of the trio that were disrupted.
- - Letting Rossi go.
Rossi was the talk of the club at academy level. Just silk and our best player at that age since the CO92 with no contest at all. He had a moderate loan to Newcastle where Glenn Roader had no idea what he was working with our how to use him. Then he came back and wasn't long before he was on his way. Rossi was honed and schooled in our ways and got the club and would have given everything he had. Plus he was a sublime talent, who went on to prove that everywhere he went until his career was taken from him as his knees blew up and then his hip.
Like others have said, Fergie earned trust to the point he was rarely doubted, and even if you did doubt, you had to wait a long, long time for the outcome one way or the other. Another thing Fergie had was a massive capacity to learn and assimilate mistakes and not repeat them. I wonder how much benefit Carrick got from the Veron episode, personally.