If we had Ugarte, Mainoo and Casemiro in a 4 3 3 formation, then Fernandes would have to be one of the front three.
That three would then be made up of three of Bruno, Hojkund, Zirkzee, Garnacho, Amad, Antony and Rashford. Too many options, we could have off loaded Rashford this window without noticing.
I suspect he plans to stick to the 4 2 3 1 (sadly!), and that Mainoo and Ugarte be the 2 long term, with Casemiro not playing as much. Mainoo still very young remember and will need a break here and there.
Bruno is then at 10, behind the striker, whoever that is, with two wide forwards from the above players.
If we were to go three centres halves with Shaw/Dalot and Mazaroui as wing backs, there are even less available slots for everyone.
Got decent squad numbers now, he's got no excuses.