FC Barcelona played just as Mourinho expected, and that's why Real Madrid's plan was so successful. Di María provided help for Arbeloa against Jordi Alba and Iniesta, and the Argentinian player delivered a brilliant defensive game overall.
Khedira and Alonso worked on Xavi perfectly, and when Messi felt like he was needed and dropped back to create some opportunities, both Real Madrid midfielders prevented him from turning to face Real Madrid's goal. With that tactical plan, Varane and Ramos were very comfortable, but they still completed a good defensive performance when needed.
But one man stood up from his teammates in Real Madrid's defensive line, and that's Fàbio Coentrao. He was left alone in Real Madrid's left back during the whole first half, having to defend Alves and Pedro both. Cristiano Ronaldo never helped him much (since he was supposed to take profit from Alves' offensive runs), but Coentrao was enough to stop two Barcelona men in that wing. On the second half, Mourinho decided to put Cristiano Ronaldo on Özil's place to give some more help to his left back, and Özil sacrificed himself defensively and helped his teammate a lot.
Real Madrid have only lost one out of the last seven Clásicos played, and that proves Mourinho is the ultimate tactical master. He has the key to stop Barcelona, but the players still need to execute his plan to perfection as they did in the second lef of the Copa del Rey tie. Mourinho has shown AC Milan how the Italian team should try to stop Barcelona. It won't be an easy task for them, but the plan is there for the taking.