It was an action-packed first half at the Camp Nou on Sunday night. Cristiano Ronaldo bundled home from close range to cancel out Luis Suarez's strike five minutes earlier.
However, as the half wore on, tempers began to flare between the two eternal enemies and reached a boiling point before the break.
Roberto and Marcelo came together just outside the Barca box and the defender reacted angrily by throwing an arm at the Brazlian.
Jose Hernandez deemed the action serious enough to brandish a straight red card and send Roberto to an early bath.
It means 'Los Cules' must play at least 45 minutes with just ten men as they look to defend their unbeaten record against a Madrid team desperate to ruin their 'invincible' status.