Since Robert Lewandowski's play at Barcelona has been outstanding, the Madrid defense needs to be extremely cautious around him. He has magical feet that allow him to score at any time.
Lewandowski is a threat to the Real Madrid defence, but I think there are many other players who can be a threat as well. Raphinha, Lewandowski and Dembele are three dangerous strikers, but Pedri and several others can also score goals. Don't forget, Real Madrid are also going through a lot of injuries so you can't really easy expect them to win at home.
Anything can happen in this el clasico, because we know that both teams have some problems with their players. The last one is Rudiger who had a problem during the game a few hours ago. I don't know much about Rudiger's injury, which was bleeding. Can he play in El Clasico or not? Because if he is absent it will be a loss for Real Madrid to lose a strong defender. Likewise with Barcelona who lost several players because of the same thing.