Barcelona head coach Ronald Koeman accepts his side cannot afford to make the kind of mistakes as goalkeeper Marc-Andre Ter Stegen did in first-half stoppage time which condemned them to a 1-0 defeat at Atletico Madrid.
There appeared little clear and present danger when the ball was cleared up field just before the break when Ter Stegen took it upon himself to rush towards the halfway line, only for Yannick Carrasco to sidestep him and shoot into an empty net.
A lacklustre Barcelona could not find their way back into the match, leaving Koeman once again facing more questions over the direction of his side, who sit 10th in the table and look well off the pace.
"We played well in the first half, but a team like Barcelona cannot concede a goal in the 47th minute as we have done," the Dutchman said.
"The players are working well, but we want better results. In principle we have done the maximum.
"Afterwards we have had two very clear opportunities to tie the game.
"But we know that Atletico defends very well. The goal was our fault, it is not good and it can't happen."
Koeman, though, did not shy away from the critics.
"Like any coach, I am responsible," he said at a press conference, as reported by Marca.
"We know that we have to improve the results and we have to trust the players I have.
"We must improve in attack or defence. We know that we need a series of won matches and must work hard to get results."
Barcelona lost defender Gerard Pique to a knee injury following an awkward fall during the second half when he tackled Angel Correa.
The club later clarified it was a right knee sprain, with Sergi Roberto also picking up a quadriceps injury.
"I do not know if the players will be out for a while. I have not yet spoken with the doctor," said Koeman.
Atletico move level with leaders Real Sociedad on 20 points after extending their unbeaten run to 24 games.
Coach Diego Simeone said: "The team is playing very well right now.
"I have been saying it for some time and it gives us confidence to keep working hard.
"When there is a link between the ideas and work on the training ground and the execution on the pitch, that is great.
"These players give their all for the team and for each other.
"Now we need to continue gathering this energy and competing well, as we have very important game on Wednesday (in the Champions League)."
