Steven Naismith putting the boot into Jonny Hayes – literally – might well have been the metaphor for Celtic’s day on Saturday.

The Hearts forward will brace himself for retrospective punishment from the SFA for his behaviour on the cusp of the break at Tynecastle on Saturday afternoon but it was a 90 minutes that knocked the stuffing out of Celtic.

Coming on the back of a week in which the civil war within the club was laid bare with little need for any imagination, going to Tynecastle and coming off on the back of an insipid performance was the last thing the club needed.

AEK Athens will have watched with interest.

Worryingly for Celtic was the performance of Jack Hendry and Jozo Simunovic at the heart of the defence. Neither looked comfortable, both were bulled and harassed by Kyle Lafferty and the fiercely imposing Uche Ikpeazu.

Ikpeazu was allowed to run riot against Celtic on Saturday. Peter Haring was given free license to pull all the strings in the middle of the park.

The former is 23-year-old who has been signed from Cambridge United, the latter is an Austrian journeyman who has found himself in Edinburgh.

As Celtic go into arguably the most important game of their season – and with ramifications that extend beyond advancing into a UEFA Champions League play-off tie – the performance was a sobering reminder of how every so often the Parkhead side fail to find their rhythm and fluency.

Granted, there were changes, five of them to be exact, as Rodgers tweaked the starting XI with an eye on tomorrow night’s game against AEK.

The game in Athens is arguably the biggest challenge of Rodgers’ tenure at the club. Certainly, tipped the balance of the tie back in Celtic’s favour in a way that enables them to progress to the play-off round will present possibly the biggest European result of his time at the club.

But the worry has to be the soft centre that proves to porous, particularly when put under pressure.

With Kristoffer Ajer suspended and Dedryck Boyata’s toys adorning the floor of the nursery there are simply no other options for Rodgers other than to go with Hendry and Simunovic at the back.

Given that it looks unlikely that Boyata will be sighted in a Celtic shirt again, there are very little options defensively. With the transfer window still open for the club, the expectancy is that there will be further arrivals to bolster those options.

Callum McGregor gave Celtic the lead in Glasgow with a superb goal but after allowing AEK to level things in the opening period there was a flatness about Rodgers’s side who seemed to become more inhibited as the game went on.

Tomorrow night will call for character and heart as Celtic look to roll up their sleeves and get on with it. But more than breaking sweat and playing with their gut, they will need to play with their heads and be aware of the dangers of going gung-ho in the hunt for the goal that they need.

Such a scenario would leave them vulnerable to a counter attack, as was witnessed at Celtic Park.

AEK are no mugs. They showed in Glasgow their willingness to sit in and stifle the game and knowing that Celtic need to score, they will set out to frustrate.

The Greek side were also far more streetwise than the likes of Rosenborg and Alashkert. AEK are a Champions League quality side and they know what it takes to get a result on that platform.

Last term they shipped just 12 goals on home soil.

It is not impossible for Celtic to go and get the result they need but they have hardly had the ideal background going into the tie.

These games are always tense. They will always carry significance given what is at stake.

But tomorrow night’s game in Athens takes on greater weight

That discord between dressing room and boardroom has added significant gravity to the game. It remains to be seen just how that pans out but it is difficult not to view it as a fork in the road.

Rodgers, though, sought to calm things down after Saturday’s game as he looked ahead to this week.

"Despite reports, there's talk of ultimatums with the board - I don't work that way," said Rodgers.

"My communication is very open, so that's certainly not the case.

"I'd read somewhere else about walking away - I've got three years left on my contract and I love every day of my life at Celtic. All I want is for us to improve every aspect of the club.

“Saturday was a disappointing result for us. We'd a good performance in midweek and drew, but you move on in football very quickly. "