Barely a year earlier, with Leicester apparently slipping out of the promotion reckoning in the First Division, supporters massed outside Filbert Street to demand O'Neill's departure. His team scraped into the play-offs, won at Wembley with a last-gasp goal by Steve Claridge, and now return to European competition after a 36-year absence thanks to the same player.
None of the victorious Leicester team last night had been born when the club made their only, short-lived appearance in continental competition. Even those associated with Leicester who do remember their Cup-Winners' Cup campaign - they qualified by virtue of losing the FA Cup final to Double winners Tottenham - could be excused for having only the vaguest memory.
After beating Glenavon, of Northern Ireland, Leicester bowed out to Atletico Madrid. A banner at Hillsborough bore the legend: "Next Stop Nou Camp", indicating that a return to Spain would be a popular destination with supporters.
But the past and the future were the last things on O'Neill's mind as he struggled to take in what Leicester have achieved in "the most unbelievable 15 months of my life". He said: "It's an incredible moment for us. The crowd have been sensational - they kept us going - but tonight was really all about my players.
"It won't sink in for a week, or a month. If we stay in the Premiership it might just sink in during the summer. I'm so pleased for Steve Claridge - his career seemed to be going nowhere before he came to us - and for my captain, Steve Walsh. He was worried about getting a crowd for his testimonial match. Somehow I don't think he'll have any problem."
If it was fitting that the long-serving, battle-scarred Walsh should have played such a vital part in the goal, it was even more apposite that Claridge supplied the decisive touch. The League Cup, as it was known before Coca-Cola and their predecessors took it on, has always been a journeyman competition compared with its FA equivalent. Claridge would doubtless own up to being the journeyman striker par excellence.
The 31-year-old, who numbers Aldershot, Weymouth, and Cambridge United among his myriad former employers, recently published a highly entertaining memoir entitled Tales from the Boot Camps. Now he has a fairy-tale ending to add to the paperback edition that will surely follow.
However, those familiar with his passion for gambling may be surprised to learn that he did not bet on himself to get the winner. "If I'd backed himself, he said, "I'd probably have missed it."
Emile Heskey was voted man of the match, though that was harsh indeed on Garry Parker, a model of industry and invention in midfield, and Pontus Kamark, who gave a remarkably disciplined demonstration of man-marking to reduce Juninho to virtual anonymity.Reuse content