Neil Lennon admits Celtic were 'poor' against Barcelona and believes a number of players let themselves and the club down.
The Bhoys travelled to Catalunya on Wednesday knowing that their UEFA Champions League campaign was over, but hoping to end it on a high.
They badly fluffed their lines at the Nou Camp, with a rampant Barca side running out 6-1 winners.
Neymar proved to be tormentor in chief for the hosts as he netted a hat-trick, but Lennon feels his travelling troops made life far too easy for their illustrious opponents.
He told Sky Sports: "Poor, from start to finish.
"There was a nervousness about us at the start, we never got hold of the ball, we made basic errors, and against a team of this quality you can't do that. As good as Barcelona were, we were very, very poor.
"I'm looking at the team tonight and there are maybe only two or three that have played anywhere near the level that we know they're capable of.
"There was a lack of desire about us tonight, which has not been like us at all.
"It's disappointing. It's disappointing for the club and I feel sorry for the supporters who have come as well. I can't accept that and we'll do something about it."
Asked if the players had let him down, Lennon added: "Not me, they have let themselves down and they have let the club down. They have let the supporters down who were here and they have let the supporters down back home.
"It was insipid, some of the performances tonight, and I have got to take responsibility because I picked the team. But they have got a collective responsibility for the level of performance."
Lennon concedes that there are few positives he can take from a humbling defeat, with Celtic outclassed and out-fought in just about every area.
He said: "I thought our heads dropped after the second goal. But going forward, we never had any passages of play really.
"We had no fight in us and no intensity to our play, which was exactly what we called for here and what we wanted.
"I can't take consolation from the game at all, apart from a couple of defensive performances - like (Mikael) Lustig and (Virgil) Van Dijk and (Adam) Matthews, for his first game in a few months, has given me a rethink. The rest were very much below-par."