Relationship with Ireland: Keith Duggan looks at the impact of a player whose fierce genius inspires love as well as loathing

There has always been a special relationship between Manchester United and Ireland, and the stunningly abrupt and businesslike departure of Roy Keane from the Old Trafford family is bound to elicit a strong reaction throughout this country.

In a year when the Manchester giants honoured the memory of Noel Cantwell, the classy Irishman who captained the team to the 1963 FA Cup, and after weeks overshadowed by the worsening health of George Best, United's immortal poster boy, comes this severance.

There was a poignancy about the fact that as Best lay hooked up to medical technology fighting to stave off actual death, the sports channels were by yesterday afternoon flooded with funereal tributes to Keane.

Best and Keane were idols for different generations of Manchester United followers, and in many respects they were polar opposites.

Best left the orange-brick terraces of Protestant Belfast. Keane fought tenaciously for a life in football from the Mayfield estate in Cork city. Best was the languid, smiling, Saturday-afternoon delight and the most potent symbol of North of England 1960s glamour. Keane was the glowering and brilliant on-field manifestation of Alex Ferguson's philosophy of the game.

He was the antithesis of the showman and, during a decade when the tabloidisation of English society lost all semblance of sanity, he fought against the celebrity machine that governs the Premiership lifestyle. Best was as affable as Keane was edgy. They were like fire and ice.

But Best and Keane were accomplices too. They were fiercely serious about their football, were in thrall to the game and shared a winner's temperament at United. They were both essentially shy men in public. And most importantly, they were Irish.

They were ours.

It has always been fascinating to see how Irish boys could arrive at the great clubs of Yorkshire, London or Lancashire as skinny young apprentices and survive to become darlings of their adopted city. Even during the most bloody and terrible years of the Troubles, odes were sung to Irishmen from England's seething football terraces.

That Best managed to seduce Manchester United with his street-artist's genius for the game and striking physical beauty meant something right across Ireland. And three decades on, Roy Keane's remarkable rise from understudy at Nottingham Forest to the voice and captain of Manchester United was an achievement all Irish sports fans, regardless of persuasion, could not but recognise.

To many thousands of sports fans in Ireland, Roy Keane's unyielding excellence and leadership in both Manchester and on countless nights in Dublin has made him a cult hero. However, his relentless intensity, unapologetic aggression and compulsion for speaking his - sometimes-caustic - mind have left many others cold.

The fallout from his traumatic departure from the Ireland squad on the eve of the World Cup set many opinions of the man in stone.

Nothing Keane could say or subsequently do - including returning to play for his country under Brian Kerr - could alter those viewpoints. And the devastating swiftness of his exit from Manchester United are bound to draw comparisons, although light has yet to be thrown on exactly why the Irishman has left his beloved club in such strange and rushed circumstances.

Love or hate Keane, he has somehow managed to become a national symbol in this country. He is unarguably one of Ireland's greatest ever sportsmen. But his influence transcended soccer and many people saw in him the best and worst excesses of the national character.

Long before the hysterical weeks surrounding the 2002 World Cup, Keane's leadership at Manchester United, particularly during his prime years, when he was a marauding suede-head bossing the action from box to box, made him a compelling figure.

He was easily the most singular figure in the Premiership galaxy, Ferguson's ruthless general, brilliant and intimidating and always, always demanding more.

Keane's uneven relationship with Ireland managers Jack Charlton and Mick McCarthy meant he sometimes received volatile treatment from the Irish fans, from whom he attracted booing long before 2002.

Even his detractors admitted he was Ireland's best player, but some were aggrieved at his perceived petulance and that his status and power meant that he behaved as an independent force, someone who came and went as he pleased. What was beyond argument was that, once on the field, he played for Ireland as though his life depended on it, regardless of where he stood in the nation's affection.

Temperamental though his relationship with Ireland has been over the years, few could have guessed the friendship, understanding and trust he shared with Ferguson for most of his adult life could turn so sharply and irreversibly.

He leaves Old Trafford as an estranged son walking out after one family row too many - and undoubtedly will leave many heartbroken people behind, in Old Trafford and across the city. Manchester has not known a split like this since Morrissey and Marr broke up The Smiths.

So Ireland awaits to see where Roy Keane goes next. Not for the first time, he has left us staggering in his wake and guessing completely wrong. As offers flooded in from Italy, from America, from Scotland and God-knows-where-else last night, only one thing seemed clear: the Corkman is a restless spirit and he won't sit still for long.