The Red Devils were humiliated at home by Liverpool at Old Trafford on Sunday, losing 3-0 in the Premier League.
While the Brazilian was hooked at halftime by boss Erik ten Hag, with United 2-0 down, his teammates came to his defense.
Portuguese playmaker Bruno Fernandes defended Casemiro in the dressing room.
To reporters, he said: "The goals are always self-inflicted. You need to commit a mistake to give them the goal. We don't need to be pointing fingers at everyone. that won't help us now.
“When you concede a goal you can't just point at one mistake. What's the point in saying Casemiro lost the ball or Kobbie (Mainoo) lost the ball? They lost the ball because they wanted to be brave. It's part of football. Don't make it individual.
"Casemiro is more experienced than me. I don't need to tell him anything, he knows what football is about. He's played for the two best clubs in the world."