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.
Meaning, like it or not, Don Carlo had to maximize his team to overthrow Barcelona with a score of at least 2-0. even though the match will be played at Camp Nou, however, Madrid has the chance to defeat the home team. the problem was, Don Carlo had to formulate a strategy to kill the movement of Barcelona's midfield players. because Barcelona's central role is in two midfielders, namely Busquets and De Jong. this duo of players as a pivot makes Barcelona stronger both in defense and plays an active role when Barcelona builds attacks.
IMO, this match is quite tough for Madrid, because, Barcelona will not let the opportunity to advance to the final round just disappear. so, Madrid had no choice but to play aggressively for and topple Barcelona. well, I'm sure this fight will present a fierce battle with high tension.
On the other hand, Real Madrid has another important match in the quarter-finals of the Champions League. against Chelsea, it shouldn't be a big problem for them even though Chelsea shouldn't be underestimated. even so, Madrid has a high probability of qualifying for the next phase. Well, before we speculate too far. Instead, we should just enjoy it when Madrid play El Clasico matches and matches in the Champions League.