In the last matchup, Mourinho opted for Fabio Coentrao on the left side over Marcelo due to injury. Should Marcelo start on Wednesday, the left side will primed for the attack.
Although Coentrao is better than Marcelo defensively and is able to keep his cool for the entirety of the match, Marcelo is much better on the counterattack and has incredible chemistry with friend and left-wing counterpart Cristiano Ronaldo. Coentrao can play on the right side if Mourinho feels he must start.
Lassana Diara also must start. Although not a consistent starter in Madrid since the arrival of Mourinho, Diara is one of the better tacklers on the team and is always running and playing hard. He, like Pepe, has been able to restrain Lionel Messi and often is able to keep his game cleaner than Pepe's.
Mesut Ozil also needs to start, too. In the last matchup, Mourinho put Ronaldo, Karim Benzema and Gonzalo Higuain in the front three. There were no true playmakers on the field. Xabi Alonso, in midfield, was under too much pressure from Barcelona to consistently make plays. Madrid were in need of men up front to dictate play.
Ozil (along with Di Maria) is one of those playmakers. Despite inconsistent performances, the German is still brilliant and can shine if given the chance. He can release Ronaldo and Benzema and open up the attack to help tear through Barcelona's defense.
Conversely, Hamit Altintop must sit. He was dreadful in the last meeting. His passes went astray far too often, he was constantly caught out of position and he hardly contributed to the defensive.