If we just look at how ETH has chosen his last starting elevens there should be 0 chance that Antony gets more then 20-30 minutes, which may be the best way for him, get his debut at Old Trafford when the fullbacks are tired and not spend all his energy first 20-30 minutes when the game will probably be tight and both teams not taking to many risks. He will be more useful in the second half.
Casemiro should be ready now, but i don't think that he and McTominey should start the game together, i would start Casemiro with Fred or McTominey with Eriksen. Casemiro showed against Leicester that his passing abilities are high, much higher then many believes because he didn't need to use them as much playing with Kroos and Modric as he will playing with Fred/McTominey. So if he plays with Fred then he will be the one trying to cut through Arsenals press, but if we continue with McTominey we will need Eriksen playing the deeper CM role next to him.
Brunos energy is needed up front, Sancho is also guaranteed a spot. I wouldn't be surprised if we start with Elanga on the right and Rashford as a number 9 the first 60-65 minutes just because of our pressing. They both will probably get instructions to press as much as possible and run their socks of before we throw in Ronaldo and Antony for second half.
Back four will not be changed if don't have no new injuries.
So will probably start with;
DDG
Dalot Varane Martinez Malacia
Casemiro Fred
Elanga Bruno Sancho
Rashford
and go with...
DDG
Dalot Varane Martinez Malacia
Casemiro Eriksen
Antony Bruno Sancho
Ronaldo
...after 60-65 minutes to try to kill the game if its still a close game. Arsenal will have to start with some players that have been injured and not trained much last week or throw in new guys that haven't played so much lately. Both ways should benefit us.
3-1. Rashford, Ronaldo and Antony to score, Casemiro MOTM.