Xavi Hernandez said the Champions League has been cruel to Barcelona this season as they face being knocked out in the group stages for the second year running after failing to beat Inter Milan on Wednesday.
Barca will be eliminated if Inter take three points from their final two games against Viktoria Plzen and Bayern Munich following a thrilling 3-3 draw at Camp Nou.
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"The Champions League is being cruel to us this season," Xavi bemoaned in his postgame news conference. "Against Bayern Munich, we were not clinical enough. There were other circumstances in Milan last week, but there is no need to talk about [those refereeing decisions], and then tonight it is down to defensive mistakes.
"Our chances of going through our very remote now. We won't lose hope, but the situation is really difficult. We no longer depend on ourselves and it is down to our own errors."
Ousmane Dembele had opened the scoring in the 40th minute in front of a raucous home crowd of 92,302, but goals from Nicolo Barella and Lautaro Martinez turned the game on its head after the break.
Robert Lewandowski drew Barca level again only for Robin Gosens to restore Inter's lead on the counter-attack. Lewandowski equalised once more in stoppage time with his fifth goal in the competition this season, but it was too late for Xavi's side.
Defender Gerard Pique had switched off for Inter's first goal, letting Barella run in behind to finish, while captain Sergio Busquets gave the ball away in the build-up to the second.
"Football is a game of errors and you have to minimise them," Xavi added. "We didn't defend well. You pay a high price for mistakes in the Champions League. Errors in defence cost us the game.
"But we are a team and if the team fails, I also fail. If Pique or Busquets or Pedri or Dembele slip up, I do too as a coach. It is my responsibility and I assume that blame."
Barca failed to make the last 16 of the Champions League last season for the first time since 2004. They now face missing out on the knockout rounds for the second year running.
Xavi says the disappointment and anger are bigger this year because, following a summer of investment in the squad, Barca have the quality to progress further in the competition.
"I am really disappointed, sad and a little angry as well," the coach said. "Last season, the feeling was that we were not good enough, but this time it has been down to mistakes.
"We had the games in our hands and we let it escape, in Munich above all, but also against Inter tonight. We have to be self-critical, too, it has been down to our mistakes.
"Last year, maybe we weren't good enough, we weren't at the required level. This way it hurts more."
Barca had 25 shots and 62% possession against Inter, but Xavi said his players need to mature in the final third.
"I agree we need to make better decisions," he said when asked about Dembele. "And not just Ousmane, when we get into final third, we all have to make better decisions, It's about footballing maturity.
"Gavi and Pedri are very young, but they make quite good decisions. Ousmane struggled more [tonight]. I have a lot of confidence in Ousmane, but sometimes he chooses badly. He stretches the pitch, he's fast and we have a lot of confidence in him."