That's a great chance for Barcelona. The hosts settle play down and start weaving pretty patterns on their right flank, eventually opening up enough space for Alexis Sanchez to surge into. The pass to pick him out is almost perfect, evading Fabio Coentrao's desperate lunge, and a last-ditch tackle by Pepe is required to claw the ball away from the Chilean before he can shoot at Iker Casillas's goal from four yards. It's a corner to Barcelona, but the delivery is easily cleared.
At the other end of the pitch, Sergio Ramos goes on a swashbuckling run that only ends when he's forced into a hilariously odd overhead kick attempt at Jose Pinto's goal. Needless to say, the error-prone Barcelona goalkeeper doesn't have too much of a problem in dealing with it, but it'll trouble the hosts that a centre back was able to cut through them so easily. Still 0-0, and halftime is only a few minutes away.
For more on the two teams, check out Real Madrid blog Managing Madrid and FC Barcelona blog Barca Blaugranes. We have live coverage of the match in our Real Madrid vs. Barcelona, 2012 El Clasico StoryStream.