Barcelona coach Ronald Koeman was incredulous after his team lost 1-0 to Atletico Madrid in La Liga on Saturday, fiercely criticising his players for switching off at the end of the first half and allowing Yannick Carrasco to score.
Carrasco made the most of several Barca players being caught out of position when Gerard Pique lost possession in Atletico's half, latching on to Angel Correa's pass and rounding keeper Marc-Andre ter Stegen, who had come flying out of his area.
"We just cannot allow ourselves to concede a goal like that," Koeman told reporters. "The goal was our mistake, you cannot afford to lose the ball like that and concede a goal so late in the half. It's always tough to create many chances against Atletico, but when you lose the ball against them you have to do better than that."
The Catalans are 10th in the standings and nine points behind second-placed Atletico and leaders Real Sociedad.
"I'm not worried about our position in the table or the league title right now, we just need to focus on winning a series of games, that's what's most important right now," Koeman said. "The coach is the number one person responsible for a team's results and I have to keep on believing in the players I have. But we have to improve things defensively and in attack."
Koeman's problems deepened with news that Pique had sprained knee ligaments after clashing with Angel Correa while Sergi Roberto sustained a thigh injury.
Barca said Pique would undergo further tests with Spanish media reporting he could be sidelined for about six weeks.
Meanwhile Diego Simeone savoured a first league victory over Barcelona in 10 seasons in charge of Atletico but refused to discuss whether the win proved his side were capable of winning La Liga.
"We have come very close to beating Barca before, we beat them in Saudi Arabia, we had drawn at their ground and lost by very little here before. Today it was our turn to win, but it won't change our objectives one bit," Simeone told reporters.
"The group is in very good shape, I've been saying that for a long time and it gives us the belief to keep working hard on what we are doing. Now we must maintain this energy and keep on competing."
Match winner Yannick Carrasco also shunned a question about Atletico's title credentials, saying his side were only focusing on Wednesday's Champions League game against Lokomotiv Moscow.
But captain Koke, the only surviving member of that title winning side, did not rule out the prospect entirely, pointing to the early season problems Barca and champions Real Madrid were having.