Even with the solid 3 points they might still not get ahead but that will close all the gap between them, let's say same point for both team on the table and with Barcelona performance recently, they should still be on the first position. 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 
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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.
...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.
I think this is the right time for Real Madrid to catch up so they have to take advantage of the opportunity to play at home to get 3 points, Imagine if Real Madrid only drew or lost in this fight then the chances would be lower in the next fight. After all Real Madrid will definitely try as much as possible because this is the first step to maintain the title. If we check the betting market, Real Madrid appears to be favored based on the odds offered.