As a sense of inevitability began to set in during the second half, there were two moments which summed up another abject performance from Celtic – and both involved Callum McGregor.
In one instance, the ball broke to McGregor on the edge of the Rangers box, only for him to be caught sleeping and duly robbed of possession.
The other saw him chasing after Ryan Naderi inside his own half and ultimately getting nowhere near the Rangers striker whose goal settled this latest Old Firm derby.
This was at a time when Celtic desperately needed their captain to stand tall and pick the team up by the scruff of the neck.
McGregor has done exactly that on countless occasions over the past ten years or so. Particularly since he took the armband from Scott Brown, he has been the totem in Celtic’s midfield. The metronome around whom all of their good play is built.
But, here, he was posted missing. Just as he was posted missing against Ferencvaros on Thursday night and against Rangers at Ibrox last weekend.
Callum McGregor has endured a bruising week with two derby defeats against rivals Rangers
He looked a pale imitation of the player who has so often dominated this fixture over recent years, with Dan Neil and Nico Raskin once again running the show for Rangers in midfield.
The current crisis which has engulfed Celtic – and it is now a crisis, of that there is no doubt – is far too complex and multi-faceted to be blamed solely on one player. But McGregor’s form has been emblematic of a team in sharp decline. The fact that Celtic remain top of the league is irrelevant.
To even mention that would be a gross misreading of this situation. Nobody should be so blinkered or naive to place too much currency on the league table.
The reality is that, as was the case last season, this is a club now in total freefall. This is Wilfried Nancy levels of nonsense. All that’s missing is a tactics board and a pair of green-and-white trainers.
McGregor’s role in this should not be underplayed. This narrative that he is so often the saviour of Celtic is tired and, at the moment, wildly inaccurate.
It’s times like these when teams really need their captains to step up but, at 33 years old, the feeling that McGregor’s powers are on the wane is hard to ignore.
The fact he called time on his Scotland career a couple of years ago was supposed to be a decision which would help prolong his club career well into his mid-30s. But the uncomfortable truth is he’s not the same player he was. A player who once was imperious in these matches now chases shadows for much of the 90 minutes.
None of this is sudden. It is the natural arc of a high-mileage midfielder who has given the club everything and routinely played well over 50 games a season.
Rangers goalscorer Ryan Naderi prepares to show Celtic skipper McGregor a clean set of heels
What is striking is how little the club appears to have prepared for it. When McGregor can’t dig them out of a hole, Celtic have no answers.
Celtic’s recent form has been a sequence of warnings rather than a sudden collapse. The Champions League play-off loss against LASK, in which a four-goal lead evaporated in the most passive fashion, exposed a fragility that has not been repaired.
McGregor himself described the team as ‘scared’ that night in Austria, an unusually blunt assessment from a captain who has rarely dealt in hyperbole over the years.
The League Cup defeat at Ibrox last week and the Europa League loss to Ferencvaros at Celtic Park followed in double-quick time.
Each time the same themes reappeared. A lack of intensity without the ball, no patterns of play with the ball, and a midfield that looked increasingly disconnected.
After the defeat to Ferencvaros, McGregor spoke of a side that felt ‘a little bit broken’ and ‘nervy’.
Perhaps most damningly of all, even after two woeful displays, there was no obvious sign of improvement from Celtic in this match. No reaction. No sense of a plan.
Martin O’Neill’s team selections are scattergun, typified by the inclusion of Luke McCowan in this match.
The system looked awkward. Celtic were caught between trying to play out from the back and going long to Camilo Duran up front.
Rangers defended superbly and mopped up everything that came their way. Dujon Sterling was magnificent, as was Olwethu Makhanya.
They deserved to win the match and, on the balance of play, it ought to have been by a greater margin than a solitary goal.
Celtic’s vanquished players troop off to the sound of discontent from the fans at Parkhead
Now only two points behind Celtic in the title race, they head into the international break with a renewed sense of purpose and confidence.
Celtic, meanwhile, are stumbling from one calamity to another. McGregor looks like a lost soul in midfield.
His diminished influence is not solely a matter of age or mileage, though both play their part. It also reflects a failure of succession planning.
For years, Celtic have banked on his reliability to paper over a multitude of other deficiencies. When that reliability is no longer there, the absence of a ready-made alternative becomes glaring.
The midfield no longer has a clear organising presence. It has no physicality or presence. The intensity that once characterised Celtic sides under previous regimes has become non-existent.
These are structural issues as much as individual ones. New signings have arrived without yet imposing themselves, none more so than Kasper Hogh.
O’Neill looks like he’s out of ideas. His experience is vast but experience alone does not automatically solve problems of coherence and basic competence.
The crowd’s frustration grew in familiar stages: restless murmuring, then louder discontent, then the kind of silence and acceptance in the closing moments that is more damning than noise.
Shortly after full-time, the supporters found their voice again, with chief executive Michael Nicholson being the target for much of their anger.
Celtic remain top of the league and still possess enough individual quality to recover momentum once they return from the international break.
But that is not the same as saying the underlying problems have been solved. The European exits, the successive heavy defeats to Rangers and the visible decline of their captain all point to a club that has lost its way.
Celtic must begin to face up to the fact McGregor no longer has the same influence on games
McGregor’s struggle is the clearest symptom of it all. A side that once revolved around his calm authority now appears to revolve around nothing at all, really.
The supporting cast has not stepped forward with the required consistency. The leadership group has not projected the same assurance.
The tactical identity, never entirely defined under recent coaching regimes, has become even more chaotic.
McGregor remains the captain and, on his better days, he is still capable of the intelligent interventions that once defined him. But the days when his mere presence guaranteed control are over.
Celtic must now confront the reality that their most dependable figure is no longer quite so dependable.
McGregor’s decline is not the sole cause of Celtic’s crisis but it is the most potent symbol.
When the player who once embodied the club’s control begins to look so hapless and out of sorts in so many of these big games, it cannot be dismissed as a one-off.
