This was slap bang in the middle of McGuinness’s annus horribilis with Donegal. The county board was scheduling too many pesky club games, his players were getting injured, and Monaghan were about to spring an ambush that would jolt the All-Ireland champions’ juggernaut into a tailspin that would end up in a hissing, spluttering heap at the hands of Mayo in the All-Ireland quarter-final.

There was no outward hint of trouble ahead when McGuinness pitched up along with Michael Murphy at a media day ahead of the big match. Malachy O’Rourke skulked around bashfully too, the Monaghan manager skilfully playing up his side as hapless meat to be fed to the hungry Donegal beast.

As I made small talk with McGuinness before our interview, attentions wandered to a bunch of kids taking part in a GAA Cúl Camp on the other side of the pitch, the sweat pouring off them as they gambolled across the hallowed turf.

“Great to see, isn’t it?” I offered, in a sort of uncontroversial I-believe-the-children-are-our-future gambit.

“I’m not sure,” McGuinness replied, “I’d question the value of that.”

I spluttered something in response along the lines of, y’know, kids playing GAA, on the famous field, er, what’s not to like?

“You have to ask what’s the purpose of it? What are they trying to achieve?”

And off he went into what I remember as a lengthy exposition on the shortcomings of juvenile coaching and youth development, how much of it doesn’t really work and ends up producing the odd talented individual with little concept of integrating a team.

I shouldn’t have been surprised. This was a man who saw things differently. After all, he’d seen potential All-Ireland champions where everyone else saw a ragtag group of messers and underachievers.

But at the time I remember thinking — Jesus, this guy must be exhausting.

What made McGuinness’s autobiography Until Victory Always one of the best of its genre was the depth of understanding it gave into the making of one of Irish sport’s most remarkable characters. You were allowed to join the dots from the grief that followed the death of his older brothers Charles and Mark, through his wild-man lost years, to his insatiable drive for success in management with Donegal.

To see the pain as fuel for the passion is to verge on amateur psychology, but you can’t help trying to figure McGuinness out simply because there is so much there to figure out. And as he embarks on his latest adventure as head coach of US soccer club Charlotte Independence, we’re still trying to figure him out.

Back when I last chatted to him, he was still in the pomp of his role as Gaelic football’s arch-disruptor. Seven years after he sent his Donegal team out to play against Dublin in the 2011 All-Ireland semi-final in a way no team had ever dared or even conceived of before, the shockwaves of that match, at once appalling and astonishing, are still being felt as the sport tries to unpick the questions McGuinness asked of it.

The notoriety he won that day never truly left him, but in truth, he simply treated Gaelic football as if it were an adult rather than a cosseted child to be nursed and protected. He subjected it to full rigour of his intellect and presented us with the results. Great innovators spawn pale imitators and McGuinness can no more be blamed for the worst excesses of defensive play than David Bowie can be blamed for the Bay City Rollers.

He upset an established order, changed the game.

No wonder Dermot Desmond took notice. Business types love a bit of disruption and the tycoon and Celtic FC majority shareholder sent McGuinness off on his current adventure when he invited him to bring his max-intensity-sports-psych-coach-guru package into the Parkhead set-up back in 2012.

And that’s how we’ve come to think of McGuinness in his current incarnation, as an adventurer. He puts one in mind of Victorian explorer chaps heading off on expeditions to chart unknown quarters of Africa. He is Phileas Fogg, setting out to circumnavigate the globe in 80 days, just to show he can. Or Ernest Shackleton, never happy unless setting sail for the deep-frozen south, the quest for the Pole a reason for living itself. The Wright Brothers, striving and straining with their experimental contraption to show that man might, one day, fly.

Donegal, Glasgow, Beijing, North Carolina, where next? Like with all adventurers, we, the earth-bound, the stay-at-home types, watch on, puzzled, amused and awaiting the inevitable crash landing. “You could just hit a ceiling,” McGuinness said this week, “and people could say, ‘Oh, that was never going to work, a Gaelic football manager? That was never going to happen’. And there are people probably waiting for that day to come.”

He knows that some people want him to fail: people within soccer, who wonder at the gall of this interloper to their world; people within GAA who reckon he should cop on and get back to where he belongs. People who can’t figure him out, who don’t look at things the way he does.

But there he goes, regardless: the adventurer, staring at the horizon and always seeing something different out there.