Manchester United goalkeeper David de Gea hit out at the schedule makers after their draw at Crystal Palace.
Casemirp picked up a booking on Wednesday night which will mean he is suspended for Sunday's huge game at Arsenal.
De Gea said: "Big blow to lose Casemiro for Sunday. I don't get it why Arsenal don't play as we have to play in the same week and they don't. Now we are missing one of our best players.
"I don't understand. Now we miss him for a big game and it is a big loss for us."
De Gea, however, was effusive in his praise for new teammate Wout Weghorst.
He added: "He did really well. On set pieces he is a big lad, he helps us in both areas and I think it was a great debut."