The Brazilian was sent off in the 119th minute of the FA Cup defeat for hitting, kicking and headbutting defender Milos Kerkez.
He has been slapped with an immediate three-match ban, which is likely to be extended after the FA charged him with misconduct for his behaviour leaving the pitch.
The head coach now insists Cunha needs the support of the club and supporters for when he returns to action.
He said: “He admitted his mistake, but for sure, he has a good personality. He’s a good boy.