Former Celtic star Chris Sutton admits the 5-1 aggregate defeat to Bodo/Glimt was "embarrassing" for the Premiership leaders.
But the club icon insists there's plenty to like about Ange Postecoglou 's side, despite consecutive chastening legs against the Norwegian champions.
The Record Sport pundit watched on as a patchwork Celtic side produced a error-strewn display as goals in either half from Ola Solbakken and Hugo Veteslen.
Despite Sutton's no-nonsense verdict, he admits there's still plenty to be positive about in Glasgow's east end despite an evening to forget.
Speaking on BT Sport, he said: "Over the two legs, to lose 5-1, although Bodo a very good team, that is embarrassing for Celtic.
"But as a whole, you have to look at the season as a whole, a bit of perspective, Ange Postecoglou has really improved this Celtic team.
"They are in with a shout of winning the league, I know a lot of Celtic fans will say you have to prioritise on winning the league going into this game, that was the priority.
"It was a poor performance, you can't get away from that."
And Sutton, in his usual devilish form, couldn't resist a quip aimed in the direction as their clash with Dortmund raged on.
When asked if a run in Europe for Celtic's city rivals would be beneficial in the race for the title, the Englishman had his say.
He added: "I always hope Rangers win.
"Oh, look, Rangers have done brilliantly. Ange Postecoglou is just going to focus on his own team.
"I love listening to him speak, he doesn't sugarcoat things, he says it as it is."
