In a word, Celtic were soft.

Many of the goals had their origins in players losing the plot in possession. Daizen Maeda did it; Alastair Johnston did it; Auston Trusty did it. Three different Celtic players did it within seconds of each other in the lead-up to the seventh goal.

The “acid test” Rodgers called this. “For us, it’s looking to bring our game to the next level,” he said on the eve of the match.

Of course, he didn’t say which direction he was thinking of when talking about the next level. Up or down?

Dortmund might have noted Rodgers’ fighting talk about how great a place the team was in (he didn’t mean Dortmund) and how he knew that they had the mentality to “hurt teams.”

Based on weekly routings of clubs with a tiny percentage of their budget. Flimsy evidence that they chose to interpret as compelling. Again.

This was a monumental humiliation for Celtic, a team that once again fell into the trap of believing that just because you can play freewheeling football against St Johnstone in Perth on a Saturday means that you can try to do the same against Borussia in Dortmund on a Tuesday.

Pragmatism? Closing the space? Staying in the fight? Keeping it tight and compact in the face of Dortmund’s obvious pace and danger? No, no. They set up like they set up against St Johnstone and Falkirk and Hibs and Rangers.

They felt they could go toe-to-toe with Dortmund because that’s what they do in Scotland and opponents fall at their dancing feet. They were pretty bullish about their readiness to transfer domestic superiority into the unforgiving fields of Europe. They’re nowhere near.

Until Rodgers introduces some overdue realism when playing some of Europe’s best, then this is likely to continue. They’ll be another shellacking down the line if he doesn’t change course.