For O'Neill, who had guided Wycombe Wanderers from the Vauxhall Conference to the brink of the First Division, it was a first taste of the unpleasant side of football management, coming only three months into the job. To be meeting Stoke City at the semi-final stage of the play-off process, therefore, brings quiet satisfaction to the former Northern Ireland international.
"The chants against myself were something I had not experienced before," he said. "It was not an easy time; I think the expression people use is 'character-building'."
O'Neill determined that pragmatism would win the day. Confident in his record as a manager, he assessed how much could be expected of him after his predecessor Mark McGhee's sudden departure and, sure he was on solid ground, fought his corner, addressing supporters' meetings and appearing on a radio phone-in.
"I always believed enough in my own ability to know that I could succeed with Leicester, given a wee bit of time," he said. "We were poor against Sheffield United. Had we been serving up that kind of football a year into my reign I would have left without being asked. But I had been in the job only 13 weeks or so."
He had inherited difficult circumstances at Filbert Street, where both players and supporters were uneasy about an uncertain future. It was two months before they won for him - against McGhee's new club, Wolves.
"There was a feeling of abandonment among the team, so much so that I feel anyone taking over would have felt the backlash from the players and the supporters," he said. "I told the chairman this might happen and it did. And at the same time I was having to make within a couple of games the kind of assessments of players that you would normally make over many weeks.
"Jimmy Nicholl at Millwall said he wished he had done things his own way from the start, and not given everybody a chance. But I did give almost everybody a chance."
In time, he sold Julian Joachim and Steve Corica, and bought Neil Lennon from Crewe, Steve Claridge from Birmingham and Julian Watts from Sheffield Wednesday. Crucially, since it was his goal at Watford a week ago that won Leicester their extension, he borrowed Mustafa Izzet from Chelsea.
It all came right after the Sheffield debacle. "We had not won in London for 15 years but we beat Charlton and Crystal Palace away in the space of five days." And before clinching their fourth play-off place in five years, Leicester won three home games in succession, their form equalling the stirring stuff of the autumn, when they led the table.
If the season has been traumatic for Leicester, it has been no less turbulent for O'Neill, who began it with Norwich, where his progress foundered on a deteriorating relationship with the then chairman, Robert Chase. He quit just as Leicester, whom he had turned down before McGhee's appointment, were reviving their interest in him. After such a time, did he not wish he had stayed with Wycombe?
"At some stages, yes. I loved every minute of my time there. I was not actively seeking a move but the interest from Norwich set me wondering whether it might be time to go. "If I regret anything it is that in leaving [Norwich] maybe I let down the supporters who felt I was championing their cause against the chairman. Leicester may or may not succeed in the play- offs, but even if we do not, I will feel we have made progress."
Charlton v Crystal Palace
Charlton will need to overcome a TV jinx if they are to build a lead ahead of Wednesday's second leg - they have not won a televised live match at The Valley since their very first - in 1947! Ndah and Dyer compete for the Palace striking slot alongside Freedman. Derby fervour will add to the tension - expect two niggly games.
Leicester v Stoke
Leicester have the quality, unfancied Stoke arguably the stronger team spirit - and they did the double over Leicester in the regular season. Stoke will field the inexperienced Whittle and Devlin in place of the injured Overson and Cranson. Leicester have no injury worries.
Bradford City v Blackpool
The fifth meeting between the clubs this season - so there could be a few old scores to settle. Blackpool may be on a downer, having just missed out on automatic promotion after occupying second place for much of the season. Bradford will be without the former Leeds winger Wright and Murray, while Blackpool have tough defender Morrison fit again.
Crewe v Notts County
Crewe made the play-offs even though they lost 10 of their last 14 games - and now they have an injury crisis to cope with. Whalley, Murphy and Blissett are all doubtful. County, who are experienced play-off campaigners, may find a role for winger Ashcroft, on loan from West Bromwich.
Colchester v Plymouth
Colchester, relishing their status as underdogs, will be far from full strength. Up front, Adock is suspended and Whitton half-fit. At the back, Caesar and Dunne are very doubtful. Plymouth manager Warnock has reached three Wembley play-off finals - and won all three. Both legs will be sell-outs, Argyle will screen today's game at Home Park.
Hereford v Darlington
Both sides are new to the play-offs but Hereford have five men who have been here before - including the prolific striker White, now 37. Darlington can boast an amazing away League record: just one defeat all season.Reuse content