Barcelona captain Andres Iniesta admitted his team's cushion at the top of La Liga was almost gone now after Saturday's 1-0 defeat at Real Sociedad.
Barca's poor run at Anoeta continued as Txuri-urdin youngster Mikel Oyarzabal headed the game's only goal on just five minutes, and despite having the majority of possession, Luis Enrique's team were unable to find a way through.
Following the draw at Villarreal before the international break and last week's Clasico defeat at home to Real Madrid, Barca have now taken just one point from the last nine available.
Their lead in La Liga is now three points above second-placed Atletico Madrid, with third-placed Real Madrid a further point back, though Barca hold the "head-to-head" tiebreaker advantage on both chasers.
Iniesta said his team had started the game too slowly and can not afford to make any more more slips in the title race.
"In the first half we did not create as we did in the second," Iniesta told Movistar Plus after the final whistle. "With the scoreboard against you, it is always more difficult. We had chances but didn't take them. We must keep going, though.
"We had this cushion to allow ourselves some mistakes, and now we have almost committed all we can."
Iniesta denied that physical tiredness was to blame for Barca having now lost two La Liga games on the bounce, after having until recently gone 39 matches unbeaten in all competitions.
"If so, in the second half we would not have pushed so much," he said. "We are playing for a lot. And sometimes it is difficult to explain a defeat with so much on the line. But it has happened.
"Things must always be analysed and on Wednesday we have another very important game."
The La Mancha-born midfielder said he still felt Barca would bounce back and prove themselves the strongest team over the 38-game season.
"Over a season there are all kinds of moments," he said. "We know this is the important phase, our cushion has reduced, but we are Barca, we still have our objective very close.
"We are still leaders, we just think about what's coming, not look back and worry about what has happened. Over La Liga the most consistent over season wins. I hope it is us."
Another La Liga loss would not affect the team as they defend a 2-1 advantage in Wednesday's Champions League quarterfinal second leg at Atletico Madrid, Iniesta said.
"This is will not affect the Champions League, it's a different competition, a knockout tie," he said. "We have a lot of experience in this. We know what is on the line, our place in the Champions League. We shouldn't dramatise the situation, and keep going."