Unfortunately, footballers are human and not always the 100% professional we expect. There will be days when players just aren't mentally strong enough or badly prepared for a game.
I never criticise Ferguson but I did see a rather predictable line up and tactics from Utd. We weren't dynamic in midfield.
But let me not contradict my post and look for reasons in the game for losing. The main reason we lost is it just wasn't meant to be our day. All the papers were talking of Liverpool crisis. So what better than a game against your arch rivals to address that.