Fabregas scored his first El Clasico league goal to seal the points
Real were three points ahead of Barca with a game in hand and Karim Benzema gave them the lead inside 23 seconds.
Goalkeeper Victor Valdes was at fault but his blushes were spared by Alexis Sanchez's drilled equaliser.
Xavi's deflected strike put Barca ahead before Cesc Fabregas completed the triumph with a diving header.
