#3 The form of Luis Suarez and Neymar
I know, I know, even Karim Benzema and Gareth Bale have been poor. But, the main difference between the two giants of Spanish football is their dependency on the front three. While Real Madrid have seamlessly interchanged BBC with the likes of Alvaro Morata, Lucas Vasquez, and Marco Asensio, Barcelona have Paco Alcacer as the only alternative to MSN.
Luis Suarez and Neymar have already scored bucket loads of goals this season (36 and 15), but the duo have struggled (according to their standards) since the PSG game.
It is a good thing that Lionel Messi is firing all guns blazing, but human as he is (I am not sure), even he might have a bad game here and there. Asking Paco Alcacer to do the business is a touch too far even for the most optimistic.