Casemiro directed much of his frustration towards Jesus Vallejo's red card after Real Madrid's 3-1 defeat to Real Sociedad at Anoeta.
Vallejo was sent off for saving Willian Jose's goalbound shot with his hand and, while Thibaut Courtois saved the resulting penalty, Los Blancos suffered while playing with 10 men.
"I think we started well and were leading the game with Brahim's goal, but the red card really hurt us," Casemiro said.
"It's difficult when you go a man down.
"Everyone in football knows it's already difficult playing 11 against 11, but with 10...
"And Real Sociedad are a great team."
The loss means that Zinedine Zidane still hasn't won away from home since returning as Real Madrid coach in March.
"There are still three points left to play for at home and we're already thinking about next season," Casemiro said.
"We have to try and do better until the very last game.
"We're working to try and improve, away from home and at home."
AN-WAR
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Real Madrid players may be tired without Benziman. CR7 absence, this season is no miracle show them. They only show hope.for fans but fail and failed again and again. Zidane what will you say about this performance?