Even someone with an ego the size of Neil Lennon's knew the game was finally up.
To borrow from Oscar Wilde, losing once to Ross County may be regarded as a misfortune; losing twice smacks of carelessness.
The Staggies now have a new claim to fame, in that they were both the first and last opponents to beat a Celtic team managed by Neil Lennon.
Their shock Scottish Cup semi-final win over the Bhoys in 2010 ruined the Lurgan man's otherwise excellent start as caretaker boss after Tony Mowbray's departure from Parkhead - and prompted the first of many 'Lenny Rants'.
The former Northern Ireland international laid into his vanquished team for exiting the competition "without a whimper" which, to continue with the morbid symmetry, was an apt description of how they surrendered their league title.
Prior to Ross County II (or III, if you include the League Cup defeat earlier this season) Lenny had been flailing around like Tony Mortana at the end of Scarface, knowing he was completely outnumbered by Sosa's heavies but too arrogant to think he couldn't shoot his way out of it.
But Lenny is no Al Pacino and, as he stood in the middle of a dark, deserted stadium attempting to explain away another defeat by the worst team in the Scottish Premiership, it was clear that the fight had finally left him.
The 49-year-old looked gaunt, shell-shocked and - unusually for him - relatively speechless.
It was no surprise when, despite vowing to see out this most calamitous of Celtic seasons, he tendered his resignation a couple of days later.
I'm glad he did, and I speak as someone who has no 'skin in the game' when it comes to the two Glasgow giants.
Lenny knew one half of the city hated him, but he thrived on that. Indeed, winding up Rangers fans was something he positively relished.
It was a different story, however, when his club's own supporters were baying for him like a lynch mob outside Celtic Park after the League Cup second-round defeat to Ross County on November last year.
Following on from another pathetic run in Europe - and with Rangers already starting to run away with slapdash Celtic's 'Ten In A Row' title dream - that was the point of no return.
The board's call to stand by one of their all-time terrace heroes was admirable but myopically sentimental; surely both parties already knew the ship had been holed below the waterline and was irredeemable.
In hindsight, a mercy-killing back then would have been preferable to the long, drawn-out, painful exit that followed.
Critics were forensic last week about the calamitous final few months of the volatile Lenny's second spell in charge - the poor recruitment, most notably out-of-his-depth goalkeeper Vasilis Barkas, the failure to cash in on assets such as Odsonne Edouard who clearly wanted to leave, the damaging fallout, both PR and results-wise, of the mid-winter Dubai jolly.
Remarkably, however, all this might still have been tolerated had Steven Gerrard not been leading the other lot on a relentlessly consistent run of victories - including in successive Old Firm derbies - that sucked the lifeblood out of their rivals.
Failing to win 11 of their 30 league games in a two-horse race is extraordinary and unacceptable by Celtic's standards, yet Lenny continued to rant and rave, defending the indefensible, blaming everyone except himself and his shockingly under-performing players for the demise and vowing, Canute-like, to turn the tide around.
It was painful to watch, and a godsend for all connected with the club when, after the longest of long goodbyes, he finally fell on his own sword last week.
The implosion and nasty denoument to his second spell in charge, which had begun in February 2019 after compatriot Brendan Rodgers suddenly upped sticks for Leicester, should not, however, be allowed to diminish the man's legendary status within the club.
Despite irretrievably losing the dressing room during the shambolic second half of last year, let's not forget that Lennon still managed to lead Celtic to an unprecedented fourth consecutive domestic Treble - and, in doing so, became the first person at Parkhead to achieve the clean sweep both as a player and a boss.
His first spell in charge yielded the first three titles of what fans believed would be 'TIAR' and the record books will remind us that Lenny was the man in the dugout when the eighth and ninth championships of Celtic's second 'NIAR' were clinched.
It's no secret, however, that a large swathe of the Hoops diehards didn't want Lenny back when Rodgers left; with a talismanic former Champions League-winning Liverpool captain installed across the city, they'd been hoping a newer, bigger nameplate would be bolted onto the manager's office door.
Instead, the board's choice of a man who had just left Hibernian under a cloud seemed both retrospective and regressive. They're unlikely to make a similar decision this time round.
I suspect that Lennon will never get the recognition he feels he deserves as a succcessful, two-time Celtic manager.
As Gers fans are wont to point out, the first three of his titles came during the period of the Ibrox club's liquidation and subsequent relegation, the fourth was prodominantly Rodgers' work and the fifth "doesnae count" with last season being truncated by the pandemic.
But you can only beat what's in front of you, and who's to say Celtic wouldn't have topped the tree in those other years anyway? Moreover, no one was decrying Lennon's managerial nous when mighty Barcelona were humbled that memorable Glasgow night back in 2012.
I do believe that, in the fulness of time, history will be kind to our boy.
He's had plenty to put up with since joining Celtic in December 2000: Northern Ireland fans jeering him at Windsor, death threats, bullets in the post, assaults on both the touchline and on the streets, appalling graffiti, vicious, unrelenting trolling on social media, Celtic supporters ultimately baying for his blood and - perhaps not surprisingly - bouts of crippling depression.
He should never have gone back into that goldfish bowl. He didn't need the money - and his Celtic contract was paid up - but perhaps someone with his mentality will always strive for adulation. It's been in critically short supply since the start of this excruciating, pivotal season.
The broken, hollowed-out Lenny of last week bore little resemblance to the chipper, chirpy, likeable and then uncapped Crewe Alexandra midfielder I first met during a Northern Ireland trip to the United States in 1994.
I remember thinking that if this young guy can play as well as he can talk, we might have something special going on here.
His immediate future, I therefore suspect, will be in broadcasting and not management; he's proved in the past to be a terrific, knowledgeable, articulate pundit. If so, it will be refreshing to hear a stress-free Lenny talking a bit of sense once again.