The Irish campaign was a series of ups and downs, and Quinn was inevitably at the centre of events.
In the midst of the Roy Keane furore, Quinn attempted to broker a deal in an attempt to see the Manchester United midfielder return to the fold.
He came close, but the negotiations fell through.
And his behind-the-scenes diplomacy temporarily annoyed McCarthy.
But, on reflection, it appears the manager realised Quinn's intentions were good, were for the country's cause.
Ireland gave the World Cup some memorable moments on the pitch.
Like Robbie Keane's last-gasp equaliser against Germany, a goal which rescued Ireland from early oblivion.
Victory over Saudi Arabia was predicted but, even so, it meant Ireland finished the group with their best points tally in the finals.
Then came that exciting last 16 game against Spain in Suwon on Sunday. Pure edge-of-the-seat sporting drama.
McCarthy, although bitterly disappointed amidst all the might-have-beens, spoke well afterwards.
He praised his players and refusing to criticise those who had missed from the spot in a nerve-wracking penalty shoot-out.
But the mighty Quinn, whose unsettling presence had once again thrown Ireland their life-belt, more than anyone put things in perspective.
Yes it was a desperate disappointment to have gone out on penalties.
But the bigger picture was in Quinn's focus, even in the instant aftermath as microphones were thrust in front of him.
Although taking his bow from the international arena - along with Steve Staunton - the magnanimous Quinn took time out to predict a bright future for forthcoming Ireland teams.
Damien Duff and Robbie Keane had already made their mark, but there were big things to come from the likes of Stephen Reid, Colin Healy, Clinton Morrison, et al.
So fair play to Quinny, a big man on the pitch and off it as well.
Memorable moments on the pitch, yes. But two off-the-field experiences will stick with me.
The street parties as millions of Koreans celebrated their team's qualification to the last 16 were truly memorable.