Sancho and Rashford aren't injured they are not playing by manager choice. I am not saying they deserve to play but I am quite sure that situation could be handled better.
I'm not sure what his issue is with Sancho and why he hasn't returned yet, but Rashford on the bench is justified in my opinion. Rashford has cost the team a lot of points this season because he is selfish and does nothing defensively; if he was at Manchester City, Pep would have kept him out for a long period.
Getting rid of the coach will only destabilize the team's rebuild, as has happened with Chelsea. The players aren't good enough, yet the managers are always punished. When will a team start firing underperforming players instead of the manager?