I've nothing against Marcos Rojo and he has been excellent in recent weeks- but I don't understand why LVG put him on against Watford.
Admittedly, the boss's hand was forced to an extent by a catalogue of injuries and when Herrera went off in the first half he had to change- but Rojo's introduction seemed an odd choice.
If there's one thing LVG ought to have learned from last season, it's that 3-5-2 just does not work with the team we have- and the loss of confidence and faith in it amongst the players was again in evidence at Watford.
At a time when United were dominating the game and Watford offering little threat, to change from a back four to three seemed odd and suggested LVG is yet to really find a system and tactical set-up he can trust.
Andreas Pereira later came on for Mata but, to me, it would have made more sense to put him on earlier when Herrera was injured.
Not only would the talented Brazilian have maintained United's attacking momentum and impetus, the change would have been more or less like for like and would have meant we could have kept the four at the back.
Even Matteo Darmian at right-back with Young moving to the wing would have been preferable, but us changing to 3-5-2 invited the hosts on to us.
After the change, particularly in the second half, our old failings with the 3-5-2 system nearly came back to haunt us- and it's a good job we managed to win as, had we not, questions would have again been asked of LVG's tactical approach.
Watford were good in the second half: they lifted the tempo, passed quicker, their movement was better and they rattled into challenges.
They got their crowd going and caused us problems and, whilst they deserve credit for that, it was as much due to our set-up and change in system as it was to any marked improvement from Quique Flores' side.
Blind was switched to left wing-back with Young as right wing-back, but the space in between them and our back three gave Watford more space and allowed Troy Deeney to drift dangerously infield.
We had not conceded for over 600 minutes so to change a previously rock-solid back four to go to a system riddled with confusion and uncertainty was risky, strange and very nearly costly.