Even the least manic of managers would have struggled to stay calm during a finale in which Leicester lost a goalkeeper, their defensive linchpin and eventually a two-goal lead but still emerged with a creditable draw from the home of the championship favourites. O'Neill seemed unsure whether to laugh or cry, but perhaps did not have the energy to do either.
The defining characteristic of O'Neill's team, like the Northern Irishman himself, is perpetual motion. There were times during the first half when they swarmed towards Peter Schmeichel, as if possessing extra men, in a manner that stunned all but one corner of Old Trafford into silence. In the end they ran out of steam, not to mention luck, though not before deepening the doubts surrounding United.
Alex Ferguson's need for new strikers is so pressing that he was prepared to test the rules concerning illegal approaches in the case of Dwight Yorke. Andy Cole's lack of involvement against Leicester highlighted why it must remain a priority, but while most of Saturday's shortcomings can be rectified by tactical fine-tuning and sharper match-fitness, one is more deeply rooted.
Eric Cantona's retirement 15 months ago robbed the United manager of a player to link midfield and the front; a catalyst with the craft to unlock the sort of 10-man barrier Leicester erected in the second half. For all that Teddy Sheringham seemed a logical replacement, he does not possess that je ne sais quoi which brought an element of the unpredictable to their attacks.
There were moments when it seemed the role was being assumed by Ryan Giggs, who perversely drifted into a congested centre when United were crying out for someone to get behind Leicester's wing-backs. Beckham, too, came infield without being able to replicate Cantona's creative authority. Until his face-saving goal, his principal contribution was a stream of crosses from too far out to trouble Matt Elliott and company.
Only in the final quarter of the contest did Giggs push into the wide position which best suits his talents and his team, although by then United looked a lost cause. Emile Heskey, surprisingly more mobile and confident than Cole, had poked Leicester ahead after being set up by the relentlessly industrious Muzzy Izzet.
Tony Cottee made up for a string of misses by doubling the lead, before Sheringham's riposte ensured that the closing minutes would take the form of a siege. Frank Sinclair was enjoying a debut to confound those who regarded him as Chelsea's weak link (in stark contrast, it transpired, with Marcel Desailly's introduction), but Leicester were already coping without the injured Kasey Keller and suddenly had Elliott helped off, too.
Finally, deep in stoppage time, a trademark Beckham free-kick answered those in the away pen who had booed him boorishly. O'Neill spoke of "a very sombre dressing-room", while his opposite number, getting soft in his old age, admitted it was "debatable" whether United deserved a point.
Ferguson's concern that they were a couple of games behind in their preparation gives an unexpected edge to tomorrow's sell-out testimonial match for the survivors of the Munich air disaster between United and Eric Cantona's European XI.
The Frenchman, incidentally, has declared his intention to play the full 90 minutes. Too much time has passed for him to be tempted back, yet his experience in dealing with the aftermath of his "kung-fu" assault on a lavatory-mouthed spectator at Selhurst Park might be of help to Beckham as he prepares to face the self-righteous wrath of West Ham's crowd next weekend.
Beckham's virtuosity, allied to poor positioning by Leicester's substitute keeper, Pegguy Arphexad, were still putting O'Neill's emotions through the wringer long after his nerves had been squeezed into submission. "My youth coach told me he'd got these two great 15-year-olds," he said, apparently apropos of nothing. "I told him I don't want to know, because by the time they're 18 I'll be dead."
Goals: Heskey (7) 0-1; Cottee (76) 0-2; Sheringham (79) 1-2; Beckham (90) 2-2.
Manchester United (4-4-2): Schmeichel; G Neville (Sheringham, 76), Stam (Berg, h-t), Johnsen, Irwin; Beckham, Butt, Keane, Giggs; Cole, Scholes. Substitutes not used: May, P Neville, Culkin (gk).
Leicester City (3-5-2): Keller (Arphexad, 60); Sinclair, Elliott (Taggart, 88), Walsh; Savage, Zagorakis, Lennon, Izzet, Guppy; Heskey, Cottee (Wilson, 84). Substitutes not used: Kamark, Parker.
Referee: N Barry (Scunthorpe).
Bookings: United: Sheringham. Leicester: Lennon, Guppy.
Man of the match: Izzet.
Attendance: 55,052Reuse content