What do you expect from fans who are desperate to see their club win a game? That come back was epic, it made the fans forget who they were backlashing and it didn't matter to them at that point, they don't mind if it was Maguire who scored as long as the goal was given and they don't care who gave the assist if it was one of their reject or not.
To me Maguire was outstanding in that game and I believe that he's one of the best when it comes to area battle in the United squad and with that assist that led to that goal ETH would have a rethink about him and the coach would try to work with him that's Maguire, to build him where he isn't good, even McTommy might see more games as it is.
I feel age is catching up with him (Casemiro) and as a club, Manchester United are expecting too much of some certain players in that squad. But the man Casemiro has given all he has to offer and playing him regularly won't make him be at his best, like you currently said he needs to be rested.
Amrabat is their and can fill in the void just to make the Brazilian (Casemiro) get himself back on track, without the coach doing this I don't think the energy he'll bring can be tolerated by the fans.
Today Maguire tomorrow Onana and the next is Casemiro, so I'd prefer ETH do some reshuffling in that team, even Rashford needs to be reshuffled from that start up 11, he has been off color, starting him from the bench is still going to help.