Martin O'Neill is a self-confessed 'muddle of contradictions' but his players always know exactly what is required of them
Watching Martin O'Neill on the touchline in Copenhagen is like waiting for carbonated bubbles to rush from within a violently shaken Coke bottle.
Sometimes there is an explosion; sometimes there is none. With O'Neill, you're never quite sure what might happen next.
And, given the uncertainty of a profession that has encompassed more than two-thirds of his life, he himself probably doesn't know either.
A self-confessed muddle of "anomalies, ironies, paradoxes and downright contradictions", O'Neill was informed from an early age by his father, Leo, that one must prepare to be confounded at every turn by life.
Always expect the unexpected. "You always think if you get a bag of sweets one day, then you're going to get knocked down by a bus the next..."
How can one possibly know a man and his life if he doesn't know the full story himself?
This quest for discovery is what drives the boy from Kilrea with the personality as unfathomable as the sea and football methods that remain, depending on your view, either indefinably complex or stunningly simple.
Russia, next summer, would be an apt destination for someone whose often inscrutable personality reflects one of her famous dolls.
He is awash with hardness and humour and can often submit both in the same sentence; even this week, he has gravitated between the gravity of a priest administering last rites to the levity of a poker-faced prankster.
Neil Lennon tells a story of meeting his then Celtic manager after loyalist death threats by telephone had effectively ended his international career, just ten years after O'Neill had been appointed the first Catholic captain of the team, at the 1982 World Cup.
"So you got my phone call, then?" O'Neill dead-panned. Only a man who once insisted his pregnant wife accompany him to the trial of a serial killer could deliver such humour from the gallows.
And yet he can be deadly serious, acutely sensitive, even - "Bollocks!"- if a former international attempts to suggest that luck intervenes in his work every now and then. O'Neill might admit it of himself but heaven forfend should anyone else.
Like his temperament, he deploys the accuracy of his memory as he sees fit; an English journalist who had closely trailed O'Neill's career in the Premier League recalled what happened when they met after a gap of several years.
"He'd just got the Irish job and when he saw me, the first words out of his mouth were 'glass half-full' and he gave me a look somewhere between disappointment and disdain. It was a reference to something I'd written years before but he'd obviously held it for all this time."
When managing Wycombe Wanderers, he took the remarkable step of penning an open letter in response to an "egregious epistle" from a critical vice-president which was printed in full - all 1600 words - in a match programme.
"I am also sorry that my substitutions and the timing of them are beyond your considerable but hardly Einsteinian comprehension," was one cutting sentence.
At Celtic, he began his media interaction by challenging the local press, and some feel his opinions of criticism have been marked by his turbulent time spent in Scotland.
Returning there two years ago, he told one of those journalists that the Irish press corps were running the Scots close in their levels of disapproval.
Even on Saturday, it seems as if his post-match spikiness was less to do with the state of the grass than media reports which had suggested he cut short Friday's training session due to fears of Danish spying.
He can harbour a grudge as much as he can harden his strongest friendships; while it often appears as if he craves publicity, the often blundering, stuttering figure who occasionally appears in the press betrays someone who is also, remarkably, quite shy.
Some recall that when feted at his alma mater, St Columb's College, his acceptance speech was quite dismissive.
Recently, at a celebration of the film, I Believe In Miracles, the story of Nottingham Forest's extraordinary rise under his footballing mentor, Brian Clough, which also featured O'Neill as a central figure, attendees recall that the Derryman barely said a word to anyone all evening.
As Roy Keane once told us, "You don't know Martin as well as you think you do, he makes me look like Mother Teresa."
Few people who interact with him ever get to really know O'Neill but he retains the ability to know everyone with whom he comes into contact.
They say great managers house 'football antennae'; in O'Neill's case, he also carries with him a constant barometer, a canny ability to gauge the exact temperature of a room and the precise requirement of an individual.
This past week, in stark contrast, say, to the trip to Tbilisi, when he bristled like a thorny briar, O'Neill has been remarkably relaxed. Before the game, at least.
He says little during the week, relying on his trusted lieutenants such as Steve Guppy and Steve Walford to take charge of training, before coming alive on match day.
Keith Ryan was signed by O'Neill for Wycombe, his first miracle-working mission, and recalls the core principles that prevailed then, and that have altered little since.
"He knows the game really well and just keeps it simple," says Ryan. "He knows when to have a go at someone, or when to put an arm around them. He can get reasonably close to people but generally keeps his distance.
"He has got friends, they're close and trusted friends. In modern day football, you have to have that. It's such big business.
"One wrong move and you're gone. So the guys he does hold close and dear are his trusted friends and he doesn't need any more than that.
"His key quality was gauging an atmosphere, calming when it is electric, stoking when too relaxed. We played in cup finals and league deciders. When he felt things were warming up too much, he could cool things down. But also motivate when needed.
"Everyone knew where they stood with him. He's the boss. I've worked with Steve Walford, played with Steve Guppy.
"The Irish players would warm to that management team. I knew they would get the job done against Wales. I'm delighted for him. He never had a chance to do it at the really highest level so it's great for him to be on the verge of a World Cup now."
Ryan recalls a league game when a combative midfielder Jason Cousins was sent off. As the team gathered at half-time, O'Neill confronted Cousins, emerging from the shower, naked, soap starching his eyes, and forcibly pushed him into the corridor.
"We can giggle about it now but I had never seen Martin so incensed. As far as he was concerned, Jason was gone and meant nothing," says Ryan.
O'Neill banned Cousins from the premises for a week but he later returned to become a club legend. The clinching coda is what happened after O'Neill's volcanic eruption. "He just calmly detailed to us the problems we were having with their left-winger, told us what we needed to do," says Ryan.
With ten men, they won 1-0.
Forty-six years spent in the professional career, 937 games as a manager, has allowed O'Neill to develop a keen instinct that, in the modern professional era, seems almost quaintly out of date.
The players he manages now wallow in an environment devoid of the incessant clipboard management that dominates the game now.
"There's nobody who knows the game better," adds Ryan. "He doesn't need the buzzwords. He knows it all himself. The game hasn't changed. It's 11 versus 11 on a grass pitch.
"Football is all about presentation now and process and buzzwords. Martin doesn't need any of that. He will still have the best analysis done and all the preparation that is required but he will use it sparingly if necessary. For he knows that sometimes a little knowledge is better than too much."
O'Neill's own quest for knowledge, his desire for discovery, at times seems unquenchable. He still firmly believes, for example, that James Hanratty, hanged for murder in England in 1962, was innocent and once made his feelings known to the trial judge.
While at Wycombe, he was entranced by the fact that the house used as the setting for the comedy classic, Fawlty Towers, was nearby and he was determined to find it.
Later, at Sunderland, the boyhood club who would represent his first failure in management - albeit one could argue that their subsequent decline shows the failure was theirs - he joined some local reporters in an emotional journey to locate the former site of the club's old home, Roker Park.
He has railed against injustice in his own life too, from the infamous GAA 'ban' that coloured his final days as a promising footballer to the desire to represent an all-Ireland soccer side that could have proved fatal to his international career.
Instead, he captained the North, a curious but brave choice by Billy Bingham within a religiously divided dressing-room that was not necessarily as joyfully united, particularly off the field, as some sepia-tinted accounts might suggest.
Throughout it all, his sense of Irish identity has remained constant; even though his daughters (who were in Copenhagen on Saturday night) have collectively spent little more than a month in the country of his birth, they class themselves, uncomplicatedly, as Irish.
O'Neill, too, is Irish, but northern.
He created World Cup history with Northern Ireland in that seminal Spanish adventure and now, 35 years on, stands on the threshold of achieving more as the Republic brace themselves for a final assault on Russia 2018.
He will not mind how ugly the battle. O'Neill borrowed so much from Clough but certainly not his commitment to style on the field, What he is committed to is the unshakeable belief that credibility only comes from winning.
Whatever about a united Ireland, in political or soccer terms, O'Neill will become a history maker tomorrow evening if he and his side can complete the job.