Well was missing so many regular starters that it can't be considered the first team. Simple as that.
DDG - Regular keeper
Rojo & Bailly - CBs with the most minutes this season
Valencia & Darmian - FBs with the most appearances this season
Pogba, Herrera & Fellaini - Midfielders with the most appearances this season
With Mata out of the picture, support for Rashford would have to be either Mkhitaryan or Lingard. Lingard has more PL starts and more appearances overall than Mkhitaryan (although Mkhitaryan has logged 4 more PL minutes than Lingard). I'm not sure either could be viewed as a "regular starter", but if you had to choose one it would probably be Lingard.
Young is the only player we have who fits into the hybrid wingback/winger role that was used in this match, so he wasn't pushing anyone out of the team.
The reality is that Ibrahimovic was the only "regular starter" displaced - and if you're looking for a speed/pressing team he wouldn't be anyone's first choice.