Luis Enrique has urged Barcelona to bounce back immediately after their 1-0 defeat at Real Sociedad blew La Liga's title race wide open.
Barca's wait for a first win at the Anoeta Stadium since 2007 was extended by Mikel Oyarzabal, whose fifth-minute header condemned the Catalan club to successive league defeats for the first time since November 2014.
The result leaves Barca just three points ahead of Atletico Madrid and four clear of Real Madrid with six games remaining.
Barca travel to Atletico for the second leg of their Champions League quarter-final on Wednesday, having come from behind to win last week's first leg 2-1.
"The game started in the worst possible way, they scored from their first chance, we had a very bad first half," Luis Enrique said.
"We needed more control. I liked the second half more. [Sociedad goalkeeper Geronimo] Rulli, as usual, had a great game. We did not deserve to lose.
"It's clear La Liga is open, exciting, but we are still the leaders and now we have to bounce back immediately."
Meanwhile, captain Andres Iniesta told Movistar: "Things are getting tighter now, we almost can't make mistakes anymore now.
"Coming from behind is always difficult. We have to continue, we have almost made all the mistakes we could have
"We are leaders, we can't feel sorry for ourselves. We have to look forward."