“Another big helping of humble pie served at Europe’s top table”

Let me start with a sentence from a former heavyweight world champion: “Everyone has a plan until they get punched in the face.”

Mike Tyson spoke about the rigors of the boxing ring. His famous quote currently also applies to Scotland's football champions.

Remember: Brendan Rodgers has never been better prepared for Champions League action. His own words. How on earth did his team, freshly boosted by recent transfer spending of over £30m, concede three goals in the space of half an hour, five goals before half-time and seven before the dismal game ended in Dortmund? put out of his misery?

The fact that Celtic lost for the first time this season at the home stadium of last season's European runners-up is nothing to be ashamed of. However, the result is very good. As well as the type of surrender.

After a 21-game unbeaten streak stretching back to early March – a relentless 20-game winning streak – it was always likely that Rodgers' men would fail in front of the famous 'yellow wall'.

Curiously, however, the result was completely different the last time the Scottish champions traveled to Dortmund. The Rangers won 4-2 against a team with Jude Bellingham, Marco Reus and Manuel Akanji.

This begs the question: why couldn't Celtic at least be competitive in the same arena?

That's the one thing Rodgers was keen to point out before a Champions League ball was kicked this time. His team is not here to take part in the tournament, but to compete. They uniquely failed to do this against a team that is currently fifth in the Bundesliga.

Of course, no panic buttons need to be pressed. After two games in the new format, one home and one away, Celtic are on three points. Exactly where they thought they would be.

The concern for Rodgers is that this was another large portion of humble pie served at the top of European football. He must have indigestion by now.

It was the third time as Celtic manager that he had watched his team score seven goals in the European Cup. Admittedly, two of them were against Barcelona and Paris Saint Germain. The big worry, however, is that this is still happening, eight years after Messi, Neymar and Suárez defeated De Vries, Toure and Gamboa at the Nou Camp.

Clearly, lessons are not being learned, which means the same patterns repeat. What is this definition of insanity again?

The impressive victory over the Slovakian champions on matchday one shows that Celtic can cope with European opponents at a certain level. Borussia's drubbing suggests a compromise will need to be found if Celtic are to emerge from the more daunting arenas with any semblance of pride, let alone points.

What do you do when the other team has better players than you?

Rodgers is a question well known to every other manager in Scotland. Now he will surely have to think carefully about this question before he next goes abroad to face Atalanta, last season's Europa League winners.

Not one of the giants of the game, but a team just as capable of embarrassing Celtic again if the Scottish champions fail to find a formula that allows them to compete with teams more accomplished and To be honest, they are technically superior.

In short: Celtic have to do something completely new on foreign soil. Hard to beat.

They are not prepared for this at home; they return to their home comfort zone without too many problems. That's what history tells you.

What the latest books also show is that the fearsome European clashes against the better-placed teams will continue unless Celtic manage to contain a backlash.

Like a boxer who takes too many punches to the face, now is certainly the time for Rodgers to let his guard down.