The Benin international was sent off for an ugly tackle on Aston Villa midfielder Yacouba Sylla on Monday night and is facing a three-match ban.
N'Diaye said: "It is a blow for us that Stephane took a red card. I think he will take three games and that is very bad for us. We have other players who can step in for him and make chances and score goals though - it is up to us to start to do that if Stephane can't play.
"I don't think it was red, a yellow card would have been fine. It is the first foul I have seen from him, because he is not a bad player for tackles. He never kicked anybody and I think yellow card was OK. A red card is bad for us.
"But we have to show that we don't rely on him. It is bad for us but we have no choice, we must keep on playing."