Barcelona manager Gerard Martino took the blame for his team's humbling 3-1 loss at Real Sociedad on Saturday.
Four days after affirming their European credentials by toppling Manchester City, Barcelona slumped to defeat and relinquished the provisional lead in La Liga to Real Madrid.
Martino shuffled his lineup from Tuesday's Champions League victory at City and tried to reinforce his defense by playing with two holding midfielders in Sergio Busquets and Alex Song.
Martino said that "having three forwards implies that we wouldn’t be playing with four midfielders. I thought that it was better to line up a double pivot, with Song.”
The move backfired when Song scored an own goal in the 32nd minute in the first of several defensive lapses that doomed the defending champions.
"Real deserved to win," Martino said. "I didn't make the correct reading of the game. The decision not to change was also a mistake."
Martino sent on Cesc Fabregas for Alex Song in the 61st minute, shortly after Sociedad score their third goal.
"We didn’t have the necessity to rethink our approach and when we decided to make our first sub, they scored the 3-1," Martino said.
The last time Barcelona lost by more than one goal was a 3-0 defeat to Bayern Munich in May 2013, but Martino said his club need "to look forward."