Casemiro is a defensive midfielder, not a playmaker. Just because Ten Hag is bad at using the tools at his disposal does not mean that the tools are bad, but rather that Ten Hag is a fool. In addition, the fouls he commits do not mean that he is to blame for them, for example recently when Onana made a bad pass and Casemiro had to make a foul to save the team from a goal, it was Onana's fault and not Casemiro.
Erik Ten Hag is among the problem of United, making poor decisions that affects the team's performance on the pitch, having issues with players and favoritism is gradually killing the fire in the Red Devils. Carlos Henrique Casimiro happen to be one of the important player for Manchester United and keyman for Erik Ten Hag. The Brazilian is known to be an aggressive defensive midfielder that have made few dangerous tackles that led to issuing him a straight yellow cards and red cards. There's more he would contributes to the team but in his absence, United defendlines seems to be more vulnerable and André Onana keeps conceding goals in every single game fixture.