Nobody trusted Valladolid's defensive system when the season started, but former Valencia defender Miroslav Djukic has been able of creating a very decent squad in which even a player like Manucho has been contributing a lot. It's true that Valladolid's defense isn't great, so that would leave Real Madrid a good chance of winning the game, but they're a good counterattacking team at home.
Valladolid's star, Patrick Ebert, came this summer from a relegated Hertha Berlin team. He has already scored three goals this season, but he's also Valladolid's heart and soul. He's a good physical player, something Djukic's team lacks. He fits his team really well, and his work rate will provide Cristiano Ronaldo a tough challenge in Real Madrid's left wing. He isn't very skillful, so Real Madrid's left back shouldn't have a lot of trouble trying to stop him offensively, though he's a good shot creator and strikes very well from distance.
Valladolid's top scorer is playmaker Óscar. He's been succeeding quite a bit against lesser teams, but facing Pepe and Ramos will surely be a different thing for him. Valladolid's midfield better be ready to work for good offensive chances, because Real Madrid is not used to concede a lot of them.
Manucho is the starting striker. He's powerful and physically ready to battle against Ramos and Pepe, but he's not very precise with his shots. Rubio and Pérez, Valladolid's pure midfielders, will try to prevent Madrid's playmakers from creating dangerous chances for their teammates. If Özil, Modric or Di María aren't having a great night, Rubio and Pérez will probably be enough to stop them and force Madrid to win the game individually, given the team's recent struggles against tight defensive lines.
Rukavina, Sereno, Valiente and Balenziaga aren't great, but neither were Betis' defensive men and they excelled against Mourinho's men. But, one way or another, it will be very hard for Valladolid's defense to completely stop Madrid's offensive rhythm.
Dani Hernández has proved himself as a good goalkeeper in this start of the season. He's good with the ball on his feet, but Real Madrid could harm him off set pieces.
Valladolid is a good team and that's why they're so comfortable in the seventh position. It'll be hard for them to keep that spot, but they shouldn't have a problem trying to avoid relegation.