Mourinho devised an excellent plan against Barcelona for the first leg, but he must consider changes in order to beat Barcelona in future Clásicos.
The three-man midfield consisting of Alonso, Pepe and Lass gives Los Blancos the defensive strength to absorb pressure and prevent Barca from unlocking the defense. However, this midfield unit does not have the ability to consistently pick out teammates and launch counter attacks.
Although Alonso is amongst the best passers in world football, Barca never give him time on the ball. The Spaniard rarely has time to turn and pick a pass, as opposing midfielders quickly close him down.
This high pressure on Alonso forces either Pepe or Lass to distribute from midfield. While they are exceptional defensive enforcers, neither have the skill or vision to consistently release Ronaldo or Benzema into space.
In order to be effective on the counter attack, Mourinho needs a central midfielder with better technical ability than Lass and Pepe. The midfielder would still track back defensively, but more importantly he would help distribute from midfield, play through balls in behind the Barca defense and ease the pressure off Alonso.
Nuri Şahin would be considered as a strong candidate to fulfill this role. However, the former Borussia Dortmund star lacks the acceleration and pace to play alongside Alonso and either Lass or Pepe. With Alonso and Şahin in midfield, the likes of Xavi, Iniesta and Messi would have no trouble ghosting past challenges and making hurtful runs into the final third.
The best option for Mourinho at this point in time is Real Madrid youth product Esteban Granero. The former Getafe player has the agility to mark Barca's midfielders and the technical skill to launch counter attacks.
Granero does not have to be a defensive enforcer, but he is comfortable tracking back and contributing on both sides of the ball.
The Spaniard has the touch, vision and skill to keep possession and pick out teammates bursting forward. Granero can also help Los Blancos in transition, finding space and playing through balls in behind Barca's defenders.
He may not be a world-class talent, but he can provide the right balance to Mourinho's 4-3-3 formation.
In order to beat Barca, Mourinho should select a more technical midfielder, such as Granero, to play alongside Alonso and either Pepe or Lass in the 4-3-3 system.
During the summer transfer window, Real Madrid should seriously consider signing a more talented central midfielder in the Jack Wilshere or Luka Modrić mold. Until then, Granero could be an influential role player against Barcelona.