If you hadn't worked it out before, the games Real Madrid played against Barcelona and Manchester United taught us all one very obvious thing—Los Blancos struggle in possession.
They're a counterattacking team first and foremost, and while deadly in quick spates, they remain a little clueless when given time and space on the ball.
It's the reason they've become over-reliant on Xabi Alonso and the reason Jose Mourinho bought Luka Modric. As a team, Celta Vigo match up well against Madrid and force them into using the ball.
It's the reason they've given them so many problems in the 2012-13 season.