"We are very pleased as we knew it would be difficult," Marcelo told AS.
"Barca is always a special game, an amazing game. We won and we played well. It's important.
"There's time to relax and enjoy the win. We're happy but we're already thinking of the next game, but we can enjoy this. We've given joy to the fans."
Real Madrid have now won their last seven league games and are only one point behind Barca in La Liga.