If you start with who got the most mins on tour, then adjust for injuries, and Maguire arriving, you get:
De Gea 255 mins
Wan-Bissaka 318
Shaw 293
Lindelof 295
Maguire
McTominay 313
Pogba 227 (Matic has more mins (306) but has benefitted from Pogba missing the last match)
Lingard 282
James 282
Rashford 336
Martial 336
Subs based on pre-season mins: Romero 195, Young 222, CB ? Tuanzebe 198 got most as CB apart from Lindelof but Rojo got more if LB mins included, Matic 306, Pereira 258, Mata 258, Greenwood 204
Players that got limited mins on tour: Smalling 135, Jones 183, Dalot 195, Chong 150, Gomes 145, Joel Pereira 90, Bailly injured 85, Fred arrived late due to wedding 132, Garner 19
We have used 4-2-3-1 for each match during pre-season, so I assume that will be our preferred formation for the early part of the season.
If you were selecting on form, rather than mins, then I think Greenwood would be a starter instead of James, while Chong and Gomes might make the bench.