For 12 years Roy Keane was an integral part of Sir Alex Ferguson's success at Manchester United, anchoring the midfield during some of the team's most successful years. However, when he left the club in November 2005, it signified a bitter divorce between the manager and his talismanic captain.
Manager Sir Alex ran out of patience for the Irishman's outbursts, where he frequently criticised his teammates in public, and their relationship came to a head when Keane began aiming his vitriol towards his manager.
In the end, Sir Alex unsurprisingly won the internal power struggle, and Keane was allowed to walk away from the club. He played a handful of games for Celtic before calling time on his career at the end of the 2005/2006 season.
Since then the pair have spent most of their time trading public barbs in their respective autobiographies. However, now Ireland manager Martin O'Neill — who appointed Roy Keane as his assistant last November — has called on the pair to see sense and reconcile.
Speaking in the build-up to his return to Celtic Park for Friday night's crunch European Championship qualifier, O'Neill said that it's time for one Ireland vs. Scotland rivalry to end.
"Manchester United have been incredibly successful and these men were two fundamental factors in this," O'Neill told The Guardian.
"If you were to ask Sir Alex Ferguson, I’d bet one of the top three or four signings he made would be Roy Keane, and he signed some very fine players. That’s how important Roy was to him. The two of them were brilliant for each other over a number of years and I think that’s something that shouldn’t be forgotten over time."
However, the Northern Irishman is unwilling to get involved in the spat between his assistant and their former mentor.
"People can have their arguments and who am I to step into anyone else’s argument, who am I to intervene? I’m not [doing] that," he said.
With Sir Alex Ferguson's famous hairdryer treatment, coupled with Roy Keane's well known hard-man persona, it'd probably be wise for O'Neill to not invite them both over for tea. Still, that doesn't dull his hope that the pair will bury the hatchet.
"I maintain is that the two of them were magnificent for each other and from an outsider’s viewpoint it’d be nice if at some stage or another they recognise that publicly. I know that deep down they know they were superb for each other.”