Atletico have had plenty of disappointing nights at the Vicente Calderon this season but this was one to remember as early goals from Diego Forlan and Simao Sabrosa earned them their third successive home win over Barca in La Liga - this time by a 2-1 scoreline.
Barca pulled a goal back through Zlatan Ibrahimovic in the first half but they could not find an equaliser and they waved goodbye to their unbeaten record.
Barca coach Pep Guardiola, whose side are now two points ahead of Real Madrid at the summit, said: "My team didn't play well, although you also have to acknowledge the performance of our opponents.
"We've lacked the control that helps us play our game. We've always been a team that ends up creating chances, and today it's been harder than normal for us due to the great job that Atletico have done.
"They've been very well organised and you have to congratulate them on the victory. We weren't sharp and we were lacking in our play and in our passing."