After 31 minutes at the City Ground, Forest midfielder Anderson slid in to try and dispossess Villa's Olllie Watkins, but, as he did, he caught the forward on the ankle with his studs up, and left him in considerable pain.
Referee Joao Pinheiro did not punish Anderson on the field and, after a very brief review, VAR Tiago Martins upheld that decision.
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It was a decision Emery did not agree with, which he made clear after the match.
"The referee was fantastic, but the VAR was so, so bad," he told TNT Sports.
"It's a clear red card. I watched it just now. I don't understand why the VAR is not calling the referee because it's so, so clear.
"I think it's a huge, huge mistake. VAR is responsible.
"The referee was fantastic, 10/10. He did a fantastic job and I appreciate a lot how he managed the match for 90 minutes.
"He could break his ankle. Wow. VAR, where are you? Please, it's your responsibility.
"You are professional, but you are doing very bad work because it was so, so clear for everybody."
