The Catalan outfit took the lead early on through Neymar, but then conceded three times without reply to lose at the Bernabeu.
"I'm clearer now about what happened last Saturday and have analysed the game in more depth. The first half was very balanced, but far from what we've been used to seeing. In the second half, when we conceded the second goal, intensified what was happening in the first half," Inside Spanish Football quotes the Barca boss as saying.
"I would be concerned if it was a question of attitude, but that's not the case at all. It was a question of football, we repeated some mistakes which influenced the game and which is my responsibility, so we'll be trying to change that. Real Madrid took the game where they wanted it, with their play."
Barcelona currently sit top of La Liga on 22 points.