The 23-year-old is a key player for the City Ground club, but may miss most of this campaign.
Manager Nuno Espirito Santo admits the club are just hopeful that surgery goes smoothly and that he can have a proper recovery.
“We miss him. It was terrible. It was a big loss for us, in terms of not having him. Now it is about wishing him the best,” the Portuguese said of Danilo this week.
“The last reports we had said it is a serious injury. But we are confident he is going to come back strong and ready to play.
“We miss him very much. Everyone loves him.
“It is always very sad when you lose a player, no matter who it is. They are always so careful about their health, trying to get all the details right ready to compete.
“When you lose one, it is very sad - especially when you realise he is going to be away for some time. But that is football and as a squad we have to be ready for it.”