With the difficult situation that Madrid is currently experiencing, their performance in the El Classico match will not be perfect, but I still believe that Ancelotti already has a plan to cover up the problems in his team, and the players will also appear all out because we know this match is full of prestige. El Classico is very profitable if they can get 3 points to catch up with the leaders of the standings. On the other hand, Barcelona, who are currently in good form, of course 3 points are also their main target. I don't think there will be a draw in the match, both Real Madrid and Barcelona have the opportunity to emerge as winners at the end of the match.
Even with the solid 3 points they might still not get ahead but that will close all the gap between them, the only way to get ahead is if they win their laliga game before the El Classico and Barcelona on the other hand lose to sevilla or share point which is on a very low probability to happen in the first place, then winning El Classico should put them on top of the table with so many ifs 
... Both side needs the three point actually, thus if Barcelona wins the game then the 3 point will create a wide gap between them giving Barcelona more chance to win the league title if it's being maintained till the end of the season.