On one hand I think a loss this big might be good, cause Fergie or the players can't smooth it all over with bullshit like "that was offside" or something like that.
The red card was so obvious that not even us, Man U-fans can deny it.
Some of the things that were wrong, as I see it:
Evans starting instead of Jones, the latter has quite possibly been Man United's best defender so far this season, and Evans is Evans.
Not the first time he ruins a game by getting sent off for something idiotic, and not the last time either.
Park starting on the bench, while I'm not suggesting that Nani is a bad player (he is probably better individually), I do think Park always shines in these kind of games, and Man United would have gotten more support on the defensive-side.
Hernandez not starting instead of Welbeck, while I don't think this really affected the outcome, Chicharito has become one of my favorite Man U-players since he joined, and I don't think Welbeck is good enough (YET) against a team like City.
He sure has the future in front of him, but a bit risky.
I do approve of the new players Man U has bought, I think Jones, De Gea and Young are fantastic additions to the team, but they didn't buy anything for the center-midfield, which is IMO the place where they need a new player the most.
I don't want Sneijder or Modric, but a bit of creativity. Like I said earlier, Özil, Hazard or Götze would have been nice, and would give the attacking-side a bit more support.
I don't think Man United has such a thing as a clear defensive midfielder either, I consider Anderson, Fletcher and Carrick fairly allround as players. They are not the best offensive midfielders, and not the best defensive ones, they sorta have qualities on both without being amazing at none.
Lastly, I don't think De Gea should get any blame, seeing as pretty much all the goals came from City outnumbering him.
Ferdinand and Evra sucked so bad today, when Man United needed a leader to emerge the most, these players just crashed and burned.