Brendan Rodgers has insisted he was proud of his Celtic players for their second-half showing against Borussia Dortmund.
Celtic were left trailing 5-1 at half-time in the Champions League tie in Germany.
A first-half hat-trick for Karim Adeyemi and goals from Emre Can and Serhou Guirassy from the penalty spot saw the match all but over at the break.
Guirassy would net a second after half time with Feliz Nmecha ending the rout with 11 minutes left in the contest.
However, Rodgers has praised his players for their display in the second half as he hailed their desire to "keep fighting" on a tough evening in Dortmund.
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"We're really disappointed with the result and performance-wise," said Rodgers. "I don't think I have been involved in a game where virtually every mistake we made got punished, that's the level.
"We could have been better with the ball but I think the early goals seemed to spook us a little bit and we didn't play with the same confidence. They were playing at a high level.
"Second half the guys showed great spirit. We had more possession of the ball and took greater risk with the ball and looked to create but ultimately we were beaten by a much better team."
The Celtic boss added: "I was proud of the players in the second half, we kept fighting and kept our spirit up.
"We will be very disappointed with the performance. It's the first time we've had this losing feeling for a long time but you have to learn from it and move on."