It is concerning that there's no clear consent on what is needed going forward. Here's my two cents:
GK- Onana* (Bayindir*, Heaton*)
RB- Mazraoui (Dalot)
CB- De Ligt (Yoro, Lindelof*)
CB- Martinez (Maguire, Evans*)
LB- Dorgu (Shaw*)
DM- Ugarte (Casemiro*)
MM- Mainoo (Eriksen*)
AM- Bruno (Mount*)
RW- Amad
CF- Hojlund* (Zirkzee*)
LW- Garnacho
This is United's current first squad. The players with an asterisk are either on their last year of contract, not good enough, constantly injured or too old. Players from the youth team (Heaven, Collyer, Obi) aren't included. Priority should be the positions with either no players unmarked, or not two players in the same position. So, GK and every forward spot. If we switch to Amorim's 3-4-3 the situation should change sligthly.
If we're going to play with a 3-4-3 next season, the situation is more dire than you're suggesting. I like Mazraoui but he's not a proper wingback; Martinez is too injury-prone and can't be counted on to be first choice anymore; Mainoo is showing some signs of being too injury-prone as well and a kid that young should never have been called on to be first choice to begin with; Garnacho is a winger at heart and not suited to playing as one of the 10s in Amorim's system.
.....................................NEW.......................................
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...............Bruno..............................Amad...................
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Dorgu..................................................................NEW
......................Ugarte.............NEW..............................
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..........NEW..................de Ligt...............Maz...............
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Five new players in the first eleven, plus a slew of new backups, is what's needed.