Marc-Andre ter Stegen has apologised to his Barcelona team-mates after the goalkeeper's mistakes helped Celta Vigo record a dramatic 4-3 victory at Balaidos, preventing Luis Enrique's men from going top of LaLiga.
The champions - who also lost at Celta last season - fell three goals behind in a dreadful first half that saw a poor clearance from Ter Stegen contribute to the hosts' opening goal through Pione Sisto.
A header from Gerard Pique and a Neymar penalty gave Barca hope in the second half, but Pablo Hernandez's header - after a more significant error from the goalkeeper - proved decisive prior to Pique's second.
That crucial goal came with 13 minutes remaining after Ter Stegen collected a backpass from Jordi Alba and proceeded to chip an attempted return straight against the head of Hernandez, who - along with a jubilant home crowd - could not believe his luck as the ball ricocheted in.
"We fought until the end, but the goal is my fault - I am really sorry for the team for what happened," the Germany international told beIN Sports.
"Clearly I want to make a pass to Jordi. It is a failure that cannot happen and again I'm sorry for the team, who fought until the end. If I had not made this decision we may have won and this was clearly my fault.
"Although this has happened I will not change my game. It has only happened once.
"It's a defeat that hurts, but we must continue. Now comes the international break and then we will try to follow the path we were on before. We must get up and go on."
Defender Pique was keen to forgive Ter Stegen, agreeing the shot stopper should not alter his ball-playing style and attempting to remain positive despite the loss.
He said: "Could Marc have risked less? Yes. But the way he plays gives us so much and often they [the risks] are good for us. He should continue [playing like that].
"With nothing to lose, we played well after the break and we almost did it. I prefer to highlight the team's reaction."
Barca are fourth in the table at the international break, two points behind leaders Atletico Madrid.