At one stage in the second period of this game Olivier Ntcham exploded the referee’s white spray when his foot planted on the dropped bottle. The explosion was notable but it will be nothing compared to the noise that will follow if Celtic do not swing the balance of this result around in Greece next week.

If things were terse between boardroom and dressing room before the game they’ll be far more strained now as Celtic stand anxiously on the precipice of the Champions League.

It is not over yet.

But the portents for the Parkhead side do not auger well in a tie in which AEK Athens have tipped the balance very firmly in their favour.

Quality was the word that dominated Brendan Rodgers’ pre-match press conference as he made clear his own irritation about the club’s business in the current transfer window. And against AEK Athens last night, Celtic came up a team that seemed like a cut above Rosenborg and Alashkert whom they faced in the earlier rounds of the qualification process.

Organised defensively and threatening in attack, AEK will feel as though they done the hard work in Glasgow.

Kristoffer Ajer, booked in the second period, will miss the game in Athens because of suspension while the streetwise Greeks will look to frustrate Celtic as they hunt for an away goal.

These nights are never for the faint-hearted.

Having got off the ideal start against with Callum McGregor’s impressive early opener, Celtic ended the night knowing that they have given themselves an uphill fight in the return leg.

Victor Klonaridis’ goal just before the interval gave the visitors a firm float to latch onto after they had looked at one stage to be sinking under a steady flow of Celtic attacks in an opening period that the Parkhead side dominated. The Parkhead side never seemed to have the same swagger about their play after the leveller.

Celtic were always willing to get on the frontfoot. In that first period they carried menace and poise. The problem was that equally they looked susceptible when on the backfoot.

On their own turf AEK will look to exploit that weak centre.

There was a surprise in the starting line up with Rodgers keeping faith with Jack Hendry and Ajer, with the more experienced Jozo Simunovic on the bench. If it highlighted his point about a lack of options, it would have been further noted as a familiar achilles heel gave the Athens side a leveller.

European ties can be topsy turvy in nature and Celtic have re-tipped scoring draws in their favour before.

But against a backdrop of internal discord and against a team who boast Champions League quality, it will take a significant performance in Greece for the Parkhead side to haul themselves back into this tie.

From the opening stages there was sense of Kieran Tierney being allowed space to roam on the left-hand side with the full-back laying down an early marker as he proved integral to Celtic’s attacking incisions.

It was the Scotland internationalist’s cross from the left that forced Vasileios Lampropoulos into a last-ditch clearance just before McGregor had an effort pushed away by keeper Vasileios Barkas after a neat one-two with Odsonne Edouard.

The pulsating start bore fruit with a goal just 17 minutes into the tie. Ajer deserved credit for his tenaciousness in winning the ball back as he initially lost possession just inside AEK’s half.

The Norwegian defender was helped out by Tom Rogic who carried the ball forward before dinking the ball to Tierney. A delicious first-touch from Tierney sent him on his way before firing the ball into the waiting McGregor in the box.

The cross seemed to take a slight deflection but McGregor’s instinct and left-foot finish as he turned his defender and rifled a ferocious first-time shot into the bottom corner magnified the important role the Scotland midfielder has taken on for Celtic.

Over the last twelve months he has developed into one of the trusted players for the big occasions, netting with a composure and assurance when the pressure is on.

As Celtic continued to probe for openings, James Forrest turned Niklas Hult inside out but dragged his shot just wide of the target as Rodgers’ side seemed in control of the tie.

But as the game edged towards the break there was the creeping feeling of AEK forcing their way into things. Helder Lopez brought out a save from Craig Gordon who had to tip his effort over the crossbar. It proved to be an indication of what was to come. It was Mikael Lustig who was caught sleeping with his malaise spreading to those around him.

Expecting a long ball forward to slide out of play, the Swede was caught out when Lopez nicked in front of him to hook a cross into the box. The Celtic defence seemed statuesque as the ball dropped and Victor Klonaridis lashed the ball past Gordon.

The crucial away goal gave the visitors fresh impetus as the game restarted. One of the first acts of the half was for Ajer to slide in on Marko Livaja with Italian referee Luca Banti flashing a yellow card at the Celtic defender.

When Konstantinos Galanopoulos was shown a second yellow for a cynical foul on Forrest, Celtic sensed fresh impetus.

Rodgers’ changes were positive as he brought on Leigh Griffiths and later Scott Sinclair. There were chances – Ntcham had a fizzing effort just wide of the target, Griffiths had a glancing header that went wide.

But as the minutes went by and the Greeks kept up the barricades the sense of ticking sounded ominous for Celtic.