If the move to 3 at the back was tactical then it is the tactics that I disagree with. We were well on top with Ander, Lingard and Memphis up front for the first half hour. Herrera got injured and we then made the change. Tactical or not, we went from playing great football to looking nervy, negative and disorganised immediately.
Watford didn't get a touch of the ball until we made that change. Herrera played well but he wasn't the only one.
It's easy to point fingers at Lingard and Memphis for poor decision making while we were playing 352. But that ignores the fact that Van Persie, Rooney, Hernandez, Wilson, Nani, Falcao and others who all have plenty of experience, have all looked poor, isolated and hesitant when playing in that formation.
The attacker receives a long ball but is all on his own. There is no width in attack and his options are really limited. Unless he does something extraordinary on his own, he will invariably end up losing possession.
I can see your point on having 3 very young lads up front, but Young could have taken Herrera's spot or Scheinsteiger could have pushed up into hole with Blind or even Jones stepping into midfield.
They might not have been perfect options but Watford weren't very good today and any of them would have been better than altering the entire shape of the side, midway through a game and to a formation everyone and his grandmother knows doesn't work.