The skipper knows every word he utters is treated with reverence by a fanbase struggling to pinpoint exactly why the dominant force in Scottish football suddenly looks so vulnerable.

To outsiders, a team that had won 16 of its previous 17 Premiership matches across the end of last season and the start of this one hardly appears to be a club in crisis.

But even before the capitulation against Linz, alarm bells were ringing among sections of the Celtic support. The issue wasn't necessarily results. It was the style of football. Games had become increasingly frantic, end-to-end affairs lacking the control that has long been the hallmark of successful Celtic sides.

The phrase "basketball football" had already entered the supporter vocabulary. Hearing McGregor use it himself was as significant as it was revealing.

More tellingly, he ventured into an even more sensitive topic. Camilo Duran and Callum Osmand, both natural centre-forwards, started in the wide positions against Linz, while Kasper Hogh was sacrificed at half-time. Yet once Haissem Hassan and Jota, two genuine wingers, entered the fray, crosses suddenly rained into the penalty box with regularity as Celtic chased the game. Hogh, meanwhile, could only watch from the bench.

Before Martin O'Neill faces the media on Friday, there is one previous exchange worth remembering.

At the end of last season, McGregor openly declared he was happy to continue his trophy-laden Celtic career, provided the club matched his ambition.

The remark prompted a memorable response from O'Neill.

“A very important player,” O’Neill said of his captain. “But a player, nonetheless. I don’t remember telling Brian Clough that we show ambition. He said, ‘I wouldn’t do, son. I would just leave you out,’ which he did do, occasionally.”

O'Neill later caveated those comments by suggesting McGregor's words may have been taken out of context.

There can be no such defence this time.

McGregor was clear, deliberate and unequivocal. Celtic are not functioning as they should. The captain has publicly acknowledged what many supporters have been seeing with their own eyes.

And that leaves the spotlight firmly on the manager.

Over to you, Martin. The response promises to be every bit as fascinating as the admission that prompted it.