I think the returning players like Ibra, Pogba and Rojo wouldn't immediately start the next few games, but their return would be beneficial to the squad as the usual busy end of year schedule would definitely take its toll on players that have been playing almost everyday from the start of the season until now. Players like Lukaku and Matic would definitely need rests in between the upcoming games.
I am not sure if Mourinho has been playing his best first 11 yet. During the 2008, SAF saved(?)/played a (then) new/different formation and system before the season comes to a close, where he played Hargreaves on the right a'la Beckham and Hargreaves for most of the season was playing in CM/DM position. Should we expect the "best first 11" to be unleashed once United is further into the CL campaign, perhaps?
If so, I think most fans especially "die-hard fans" of Rashford and/or Martial would get to see both of them starts in the attacking 433 formation, with Mata as the AM/no. 10 behind the trio of MLR, shielded by both #AgentP and Matic.
Either way, can't wait to see the whole squad to be fit and ready. I think teams like Spurs, Chelsea and City have been pretty lucky with the injuries so far this season.