The Brazilian midfielder was sent off for a clumsy tackle in Manchester United’s home 0-0 draw against Southampton.
Referee Anthony Taylor at first booked the 31-year-old, but eventually changed his mind after re-watching the challange on the screen, aided by the video assistant referee.
Despite manager Erik Ten Hag being furious at the decision, the team believe there is very little chance of the red card being overturn.
“Casemiro is across European leagues, in over 500 games he had never a red card and now he has twice,” United manager Erik ten Hag said after the Southampton game.
“He plays tough but he plays fair, also in this he is playing fair. Same as against Palace, so it is very debatable.
“When you freeze it looks bad, but everyone who knows something about football, who is acting on top football, they know what is bad and what isn’t bad, what is fair.
“I tell you, Casemiro is a really fair player. Tough but fair and it shows over 500 games in big leagues, never sent off.”
Defender Raphael Varane added: “He’s a player who’s very important for us. He brings balance to the team and to the squad, but we have a great squad and we have to find another balance without him.”
“But we have good players in every position on the pitch and we’re ready for the next games.
“I think he was very disappointed because nobody wants to get out of the pitch before the end but as I say it’s part of football.”
Casemiro is due to serve a 4-match ban, with the extra game coming as this is his second straight red of the season, after sending off against Crystal Palace in early February. That means the Brazillian will miss FA cup quarter final against Fulham and Premier League games against Newcastle, Brentford and Everton.