Hall of Fame... Roy Keane: He's always spoken his mind but on the pitch his feet did the talking - this all-action hero could do everything (including taming Vieira)

Seeing red: One of Keane's many dismissals in a United shirt, against Blackburn

Early days: A young Keane of Nottingham Forest looks on as Paul Gascoigne sits injured on the Wembley turf during the 1991 FA Cup final

One night in Turin: Keane put in probably his most memorable United performance at Juventus, when he led them to victory despite knowing he would miss the final through suspension

FA Cup of joy: Keane lifts the famous old trophy after United's win over Millwall in 2004

Strike: Keane fires home against Fiorentina in the Champions League in 2000

The power and the glory: Keane holds the Premier League trophy aloft in 2003

Greats united: Keane and Eric Cantona (right) are still both revered at Old Trafford

Sign of the times: The United fans show Keane their gratitude with a banner at Old Trafford

Green giant: Keane was the Republic of Ireland's best player for more than a decade

There were a number of outstanding performers in United’s Treble-winning season but it is hard to imagine that team without Keane, the on-field driving force of a side that simply refused to yield.

He played as though he would walk through plated glass for Ferguson, just as he did in the qualification process as Ireland reached the 2002 World Cup. His performance in Turin, where United overturned a 2-0 deficit to win 3-2, has become the stuff of legend.

Having been cautioned, knowing he would miss the final, Keane stretched every last sinew for the United cause, outplaying Zinedine Zidane and Edgar Davids to lead the fightback against Juventus.

If this was the game to define his career, then his rivalry with Patrick Vieira and Arsenal could not be far behind. It was the confrontation that scripted a decade of compelling viewing. Keane v Vieira. Manchester United v Arsenal.

By the standards of hatred, tension and aggression set by those old foes, today’s headline rivalries feel anaemic, prissy and sanitised.

Best of enemies: Keane and Patrick Vieira enjoyed the Premier League's most famous rivalry

Tunnel vision: Keane and Vieira have an argument before a Premier League match in 2005

Another spat: Referee Graham Poll has to step in to placate Keane after another argument with Vieira, in 2005

Head and shoulders above: Keane and Vieira were the dominant midfielders of their Premier League era

Clash of the titans: Keane and Vieira once again do battle in the 2004 FA Cup semi-final

TV stars: Keane and Vieira in a promotional picture for the documentary 'Best of Enemies'

 

Roy Keane and Patrick Vieira face off in tunnel before kick off

There were, of course, times that Keane went too far, a law unto himself. We cannot ignore his moments of lunacy, which verged on that of a sociopath. The knee-high smash into Alfe-Inge Haaland, the stamp on Gareth Southgate. The truth is that behind the icy visage, few knew what the real Roy Keane was capable of.

But despite everything, despite that toxic war-of-words with Ferguson - ‘The hardest part of Roy’s body is his tongue,’ the former United boss notes in his autobiography - still his name is sung with gusto at Old Trafford, still the Stretford Enders remind the world that ‘there is only one Keane-O’.

Behind the psychotic image, there is a charismatic, boyish vulnerability that lingers in Keane but he is revered most for his unflinching principle.

The United supporters adore his frank appraisal of the Glazer family ownership model, his brutal criticism of the prawn sandwich brigade at Old Trafford and his cutting takedowns of the flash Harrys in the changing room with Lamborghini mentalities.

Disgraceful: Keane deliberately puts in a despicable challenge which broke Alf-Inge Haaland's leg

Revenge: Keane aims a volley of abuse at the stricken Haaland after the tackle

Stamp it out: Keane stands on Gareth Southgate's chest during the 1995 FA Cup semi-final replay

Dog days: Keane walks his pet Triggs in Cheshire after leaving the Republic of Ireland 2002 World Cup squad following a bust-up with manager Mick McCarthy (right)

Swing and a miss: Keane throws a punch at Newcastle's Alan Shearer during a disagreement

Writes and wrongs: Keane (left) has to be held back from Jason McAteer (right) after the Sunderland midfielder told him to put any insults 'in his next book'

 

Ferguson: Keane overstepped the mark criticising his teammates

It still seems a shame, though, that this curious man’s most telling contribution these days is from a studio, rather than the dugout. And you sense Keane sometimes wishes he was still out there, still in the thick of it. This, after all, was his assessment of punditry back in 2008: ‘I’d rather go to the dentist. You’re sitting there with people like Richard Keys and they’re trying to sell something that’s not there.’

For much of his career, remember, we speculated on how Keane could become a manager of elite-standing, demanding only the best of those around him. A graduate of the teachings of Brian Clough at Nottingham Forest and Ferguson at United led many to predict a glorious second career for the Irishman.

Then again, maybe it was always inevitable that Keane would be frustrated to manage other human beings that lacked the extraordinary levels of determination that his soul boasts in abundance.

Wonderland and Blunderland: Keane's first managerial job was at Sunderland, who he got promoted in his debut season but it went downhill from there

Unhappy Town: Keane was manager of Ipswich but it was an unhappy spell

Glamorous assistant: Keane is now No 2 to Martin O'Neill (right) as Republic of Ireland manager

 

Roy Keane: I'm not an animal that needs taming

Keane, though, was always set on coaching. At United, he would help out with the younger age groups and he was engrossed in the Pro-License course that he achieved at Warwick University.

We should hope that he can impress alongside Martin O’Neill in his new assistant manager’s role for the Republic of Ireland, for Keane must surely still have something more to offer the game than this ruthless score-settling on national television.

His appetite for football remains undiminished and who knows, maybe one day, a brave chairman will find a place for Keane to dine at the top table of this sport once more.

Talking a good game: Most of Keane's best work now is done in an ITV studio as a football pundit

 

Roy Keane criticises Carrick's post-match Olympiakos interview

A smile! Keane enjoys a day at Chester races with David Beckham and Nicky Butt in 2003