Champions League: Borussia Dortmund v Celtic

Date: Tuesday, 1 October Venue: Signal Iduna Park, Dortmund Kick-off: 20:00 BST

Coverage: Commentary on BBC Radio Scotland, text updates on BBC Sport website & app

Having faced some lightweights so far this season Celtic are now entering an altogether different division - a Champions League game against last season’s runners-up in their own storied ground. The “acid test” as Brendan Rodgers is calling it.

In boxing parlance, we’ve had an undercard that’s lasted weeks, a series of mismatches that Celtic have won with a remorseless intensity.

Scotland is a comfort zone for Rodgers’ team. Very little about Dortmund on Tuesday is expected to be comfortable.

Dortmund are not in a great place right now, but these things are relative. They finished fifth in the Bundesliga last season - their lowest placing since 2015 - and only qualified for the Champions League because Germany were given an extra spot.

Of course they made the Champions League final, but they were fortunate to go that far. In their semi-final Paris St-Germain hit the woodwork five times over two legs.

And the team that started against Real Madrid in the final? Mats Hummels, Jadon Sancho and Niclas Fullkrug have all moved on. Marco Reus and Sebastian Haller got game-time as well but neither of them are there now.

In recent weeks they’ve conceded two goals - in a 4-2 win - to Bochum, one of the weakest teams in the league - and they lost 5-1 to Stuttgart five days before.

As one Dortmund observer said on Monday, they’re capable of incredible sloppiness and they’re unsettled in defence, but they’re still Dortmund and still dangerous when the mood hits.

They’ve had two different right-backs and three different left-backs in their past three games and the word is that Niklas Sule is going to start at right-back against Celtic. The musical chairs look set to continue, which might sound pleasing to the ears of Celtic’s front three.

Daizen Maeda’s work-rate, Kyogo Furuhashi’s movement and Nicolas Kuhn’s creativity have garnered 14 goals and 12 assists between them so far.

Celtic will try to unleash the hounds but attacking verve alone will get them nowhere on Tuesday.

Unless it’s accompanied by dogged resilience then they’re done for. Too often on nights like these, staying in the fight has not been a Celtic strength.

It’s been a dozen years since Celtic defied expectation and won a Champions League game of this magnitude. ‘Watt’s the story, Celtic’s glory’ and all of that.

That win against Barcelona in Glasgow, secured by a young Tony Watt, was a footballing miracle built on four attempts on goal to Barca’s 18 and on 27% possession to Barca’s 73%, but there’s been nothing like it in the years since.

Celtic’s relevance in Europe for a decade and more has been around the atmosphere in their stadium rather than the quality of their team. Visiting players have showered their fans with praise for creating world class atmospheres, which was nice, but almost galling at the same time.

Celtic shouldn’t really want to hear what a lovely time the great and the good of European football had while playing in Glasgow - or anywhere else. When they start saying what a misery it is to play against Celtic then a corner will have been turned.

Maybe that’s Tuesday evening. Seeing is believing, of course. The loss of Cameron Carter-Vickers puts the brakes on the optimism to a fair extent, given that the centre-back is the one who ties it all together at the back.

There’s also the task of Celtic having to go up a couple of levels from what they’re used to and then staying at that level for an entire evening when Karim Adeyemi, the flying machine winger, and Serhou Guirassy, the excellent finisher, are beginning to motor.

This is Rodgers’ 20th full Champions League game as Celtic manager. There’s no marquee victory on his record, no win that reverberated around European football.

This would be it. Against Dortmund, we’ll find out more about Rodgers’ side - flat-track bullies or something more significant?