The Blaugrana were handed their third league defeat of the season at the hands of Atletico Madrid on Saturday to trail top spot by a mammoth nine points from tenth place.
"It is worrying," he told Movistar, as per Goal.
"For a big team, conceding a goal like this ... it can't be, because it's the 47th minute, we had the ball and then they score, 1-0.
"We controlled and we knew that it was difficult to create many chances. We had a pair and with the score 0-0, the game would have been totally different [if they had taken either chance].
"Like any coach, I am responsible for the team's results."
1. Manchester City – €1.063bn / R20.1bn
2. Paris Saint-Germain – €888m / R17.2bn
3. Manchester United – €844m / R16.3bn
7. Liverpool – €666m / R12.9bn
10. Everton – €504m / R9.7bn
5. Chelsea – €763m / R14.8bn
9. Arsenal – €590m / R11.4bn
8. Juventus – €594m / R11.5bn
4. FC Barcelona – €826m / R16.3bn
6. Real Madrid – €708m / R13.7bn