It doesn’t matter what sort of form they are in, or where they sit in the league, this game is always the biggest in Europe when it comes around.
And the fact that these two are just one point apart, coming into the final furlong of La Liga campaign, means that there is more resting on this one than ever.
Barcelona started the season well and then lost a few. Since then they have steadily improved and look in their best form of the season, with Lionel Messi approaching his very best and players like Ivan Rakitic showing that there is life after Xavi in the midfield. With Neymar likely to recover form a knock, Barcelona look strong.
But while Barcelona look settled Real Madrid are anything but. It’s the most dramatic club in the world and opinions about the team can change vastly almost overnight. But even an understated view on the Real Madrid status quo would point out that there has been a worrying loss of form since the turn of the year.
They crawled through into The Champions League quarter final after losing at home to a very average Schalke side. And the magical formation from pre-Christmas looks clunky and uncertain right now. James Rodriguez is still doubt but but the return of Modric could prove to be the missing ingredient and get Real Madrid motoring again.
So the form book says Barcelona, who also have home advantage. But, as we well know, anything can happen in these mammoth matches. Roll on Sunday.