Madrid are absolutely ruthless on the counter and in quick transitions. And after their horrendous league start, they will have a point to prove infront of their own crowd.
What Madrid aren't good at is proactively creating something against teams which keep it tight at the back and don't afford them space. Madrid's main weakness: Xabi Alonso. He is horrendous when getting pressed but he's also the only player who dictates their whole game structure. In the Sevilla game Rakitic constantly harrassed him and they were all over the place. They are a counter attacking automaton. They lack the flair to break teams down without running into space. Which is why they bought another central playmaker: Modric.
Ronaldo is harmless 1 on 1. Forget the media hype. With the ball at his feet he creates absolutely nothing. It's Özil, Di Maria and Benzema who are dragging defenders out of shape with their movement for Ronaldo to cut inside and tap-in the chances they create. So rather concentrate on the suppliers further back. Alonso and most likely Modric in this game.
Another weakness will be Ronaldo's lack of backtracking. Silva and Tevez drifting and overloading Coentrao's side would cause them all sorts of problems.
You should also put pressure on their centrebacks. They are prone to hoofing it up. Is Agüero match fit?
Maicon would be a desaster. Mourinho knows him inside out.