Perhaps they were going for a fair play award.

In a bid to make things interesting after the 5-0 win in Glasgow, Celtic headed into the return leg against Astana with no central defenders. It most certainly added a layer of intrigue to the evening.

With Dedryck Boyata and Erik Sviatchenko injured and Jozo Simunovic’s knee toiling with an artificial surface - despite internet rumours there has been no bid received for Simunovic - Celtic went with a central pairing of Nir Bitton and Kristoffer Ajer. It is safe to see that it is a partnership unlikely to be aired again any time soon.

Read more: Celtic manager Brendan Rodgers: This was our annual Be'er Sheva moment but the players were magnificent

The entire idea of the 5-0 victory a week ago was to preserve fingernails and keep bums on seats; instead as this frantic second half progressed, Celtic found themselves on the edge of one.

Rodgers has created records and stats too numerous to mention in the relatively short time that he has been in charge at the club, but there were points in this game when the Hoops might have feared that they could become the owners of an ignominious one; no team has overcome a 5-0 deficit in the Champions League qualifiers.

The loss of their unbeaten record in all games, a run that stretched all the way back to a November defender in Glasgow to Barcelona, will seem like small price to pay for getting into the group stages, especially after just how difficult Celtic made it for themselves.

The story of this game was essentially encapsulated with the impressive Olivier Ntcham’s 80th minute goal, a goal that punctured the building, antsy pressure on Celtic.

The Hoops bench rose to salute the goal with the generally impassive Rodgers leading the celebrations. Little wonder.

It was way more pressurised than it ever needed to be, largely down to sloppiness and defending that would have been out of order in the nearest primary school’s play-time kickaround. Certainly, if someone had suggested that there were ten minutes until the whistle the expectancy might have been for at least another half a dozen goals.

Read more: Celtic keep their cool to book Champions League place

There were times when the ball dropped deep in the Celtic box and one might have wondered if a rattlesnake had fallen from the sky, such was the reluctance of the backline to attack it.

There was an uncharacteristic reticence that was entirely out of sync with the intense, aggressive game that Rodgers has implemented at Celtic.

Ntcham’s goal and then Leigh Griffiths strike in the final minutes of the game allowed Celtic to breath but there was a half-hour period in which every time they exhaled, they seemed to leak a goal.

It made for an evening of entertainment, entertainment at the cost of soaring blood pressure for those of a green-and-white persuasion, but this will be a night that will underline just what work still needs to be done for Celtic.

Rivaldo Coatzee’s arrival is imminent but with finances assured now that progress to the Champions League has been clarified, Celtic will want resources to cope with a two-pronged domestic and European assault.

Certainly, the arrival of another defender couple of Boyata's emerging fitness ought to eradicate this kind of experiment by the time the group stages get underway. but last night's display may also have exposed a layer of vulnerability to Celtic that has not been glimpsed over the last year or so.

There was a fragility to their lead and to their mental state of mind, a glimpse of something that seemed to be cosigned to a previous era.

The temptation will be to dismiss the result as a freakish night in which Astana came at Celtic with absolutely nothing to lose on a night when Rodgers' hand was forced through injury issues.

Read more: Celtic manager Brendan Rodgers: This was our annual Be'er Sheva moment but the players were magnificent

But the smart money will be on absorbing the lesson that was there to be learned.

Celtic will face teams with far greater might than Astana in the Champions League group stages. This is a season when they hold ambitions to put down their own calling card in the tournament.

Doing so will require that there is no repeat of the deficiencies that were brought to the fore against the men from Kazakhstan.

As the whistle sounded on this game, there was something telling in the reactions to the Celtic players. So often the clarification to the group stages of the Champions League is met with wild celebration, as well it might given what it means.

But after a first leg trouncing and the perilous nature of what threatened their equilibrium last night, it was sighs of relief which echoed amongst the Celtic players rather than the whoops of delight.