The more I've thought about this game, the more I'm thinking it'll be a far stronger side than I initially expected.
The only players that made it to the quarterfinals (played 10-11 days ago) were Maguire, Shaw, Dalot, Malacia, Casemiro, Fred, Bruno, Antony, Rashford, Martinez and Varane.
A large amount of those players didn't necessarily play huge parts in those latter stages either. Only Dalot, Shaw, Casemiro, and Bruno need to be considered for resting IMO (Martinez & Varane obviously as well). Maguire hasn't played much earlier in the season so should be expected to come right in.
We will likely see a second choice back four. Maybe Donny over Bruno. The midfield two could realistically be any from McTominay, Eriksen, Casemiro or Fred. Front line might be strong, Martial should start but the other positions could be any two from Rashford, Antony, Garnacho or Elanga.