The obvious answer is: exactly the same as against Arsenal! Nobody touch anything! It's all working okay!
However, there are a couple of considerations that might lead to changes. For a start, Watford may not be technically as good as Arsenal, but they're almost certainly more sensible. And for a finish, a couple of United's injured players are back in contention. It's a miracle.
The most notable is Anthony Martial, who limped out of the warmup before the game against FC Midtjylland and inadvertently kickstarted The Marcus Rashford Extravaganza. The Frenchman will have to come back in — his dribbling will be needed against a more defensive, less hilarious opponent — but with his emergency replacement having scored four in two, it looks like Martial might have to operate from one of the flanks. We're predicting Jesse Lingard to drop out and Memphis to move over to the right.
The midfield stays as it is. No meddling, Louis.
At the back, there are suddenly options. Options! Marcos Rojo's injury wasn't too serious — according to Van Gaal, it was "only a kick" — so we're predicting that he and Guillermo Varela will keep their places, and Matteo Darmian will only make it back as far as the bench. For 20 minutes. Until Varela limps off. Chris Smalling will apparently be assessed closer to kickoff, but if he's even three-quarters fit, he'll probably replace Michael Carrick as both captain and central defender.
So, something like this ...
Subs: Sergio Romero, James Weir, Matteo Darmian, Michael Carrick, Timothy Fosu-Mensah, Jesse Lingard, Adnan Januzaj