It won't be very good for Real Madrid if they become out of the Copa del Rey as well. Because they have already lost most of their chance to win the La Liga title. If they get eliminated by Barcelona in the Copa del Rey as well they will have only the Champions League left. Finishing the season without a title would be really bad for Real Madrid.

Barcelona can really push them out of the Copa del Rey by the way. Because they already beat them in the Santiago Bernabeu in the first leg. I think they would finish the incomplete job.