After throwing away a 4-0 aggregate lead, Celtic will now compete in the Europa League When Callum McGregor eviscerated his own team-mates in the wake of Celtic's stupefying Champions League collapse against LASK, he delivered their one coherent moment of a spineless night.
In branding his fellow players "passive" and "scared" and in then sending a telling shot across their bows - "now we'll see what people are made of" - it is hard to recall him being so full of fury after a European game.
And there are plenty to choose from, plenty of dark nights, plenty of embarrassment, plenty of soul-searching over many years. For close to a decade he has been Celtic's best player, a near ever-present.
That longevity has brought him many trophies, but he's been around for many mortifications, too. Where losing a 4-0 advantage ranks in the pantheon of Celtic failures is a moot point.
What is unarguable is that it was a total capitulation, a feeble collapse in the face of LASK's physicality and desire and belief. O'Neill takes responsibility after Celtic's latest European capitulation Exhausted & fragile - how Celtic's capitulation unfolded Celtic blow four-goal lead to LASK in Champions League collapse The Celtic captain called his players "scared" when winning 4-0.
No media hatchet man could come up with a more damaging word to describe what happened out there. He was there last season when Celtic's fecklessness saw them go goalless for 210 minutes against the popgun boys of Kairat Almaty before failing to score from three of their five penalties in the shootout.