If the true nature of the enmity between Sir Alex Ferguson and Kenny Dalglish still provokes a hundred theories on the eve of their latest confrontation, there is also a strong suspicion of where its roots flourished most vigorously.
It still lingers powerfully that it was in the fetid, gang-infested new town of Ciudad Nezahualcoyotl on the edge of Mexico City 25 years ago where Ferguson's unabashed admiration for the brilliance of his fellow Glaswegian congealed into an unshakeable resentment or, if not that, the keenest of regret.
One thing at least is beyond question. No football manager ever yearned more for the services of a single player as Ferguson's Scotland, his inheritance from the beloved hero and mentor Jock Stein who died of a heart attack on the road to that World Cup, sought the single goal against 10-man Uruguay that would have carried them into the knockout stages for the first time.
Down all the intervening years the issue of Dalglish's absence that day remains so delicate that in his forthright autobiography Managing My Life the Manchester United manager carefully quoted from his rival's life story when he addressed the question that still haunts Scottish football history.
Did Dalglish advance the time of a knee operation – and withdraw from the Scotland squad – out of the strictest medical necessity or in protest over the exclusion of his Liverpool team-mate and great friend Alan Hansen by Ferguson, who decided in favour of his Aberdeen stalwarts Alex McLeish and Willie Miller?
Dalglish's denial is emphatic but this does not reduce the fascination of re-reading Ferguson's account of the episode.
Ferguson recalled: "Having weighed and sifted all the evidence to the point where my squad was virtually complete, I came back to the thorny question of Alan Hansen. In fact it had ceased to be a question. I was leaving him out. I had not looked for a reason to do so. I had never fallen out with him and had no axe to grind.
"My criteria were strictly those of a football manager and there's no contradiction in adding that the memory of how Alan dropped out of the game in Cardiff [where Stein died] and then the England game loomed large in my thinking. I simply felt that he did not deserve to go to Mexico. But I realised that Kenny Dalglish would take a different view and made sure he was the first player I contacted on the day before the squad was announced.
"After telling him how pleased I was he would be with us, I gave him the news that I would not be taking Alan Hansen. Kenny made the expected response. He said, 'He's a great player – you cannot leave him out.'
"Shortly before we were due to fly out, Kenny called off. We were informed that he was going in for an operation on his knee."
Later, Dalglish wrote: "People claimed I was snubbing Fergie out of spite over Alan. That was not true. Those who said I pulled out because Alan Hansen wasn't picked were not only libelling me but impugning the integrity of the surgeon who told me not to go."
Ferguson, who was later frank about his unhappiness with some aspects of his own performance in a Group of Death that also included West Germany and a brilliantly promising Denmark, contented himself with a series of sighs – and the comment, "His extraordinary talent was matched by unbreakable courage, an attribute the importance of which is often overlooked when great players are dazzling us with their skills.
"Kenny was physically and mentally tough and he had an aura around him that would have been priceless in the Scottish camp."
That makes two auras at Anfield tomorrow – and the riveting sense that neither of them can often have been in quite so pressing need of such reinforcement.
It is one of the redeeming beauties of football that it can so frequently throw up such pivotal set-pieces requiring so much nerve and belief in how the game should be played.
Ferguson has to kick hard and re-start the drive for his 12th Premier League title that wobbled, after a fine first-half display, with defeat at Chelsea on Tuesday. He has to discourage again an Arsenal maybe psychologically vulnerable after their failure to end the six-year drought of trophies against Birmingham City in the Carling Cup final last Sunday and faced with another ordeal by fire at the Nou Camp.
Dalglish has to hold together a Liverpool hugely heartened by the return of that aura, and the re-imposition of some classic values, but bruised by a defeat by lowly West Ham last Sunday and its reminder that for the moment at least the essential task remains one of damage control.
After all these years of mingled respect and animosity, Ferguson and Dalglish are locked together by some of the game's most basic imperatives. Ferguson, 69, Dalglish, nearly a decade younger, must do what all football men have to sooner or later, whatever their previous success. They have to re-make teams, give them new impetus, new reasons to believe that they can succeed.
In both cases – they have no doubt already told their American owners – the re-seeding will necessarily be expensive. Both need players of world-class talent and powerful influence. With Paul Scholes draining the last of his good red wine, and Ryan Giggs also contemplating rather less than a half-filled glass, Ferguson needs a major midfielder, a man the team can look to when something extra is required. Such a player was required at Stamford Bridge when Chelsea came back to United and he simply was not there.
Dalglish's requirement is also self-evident. Steven Gerrard remains capable of erupting brilliantly from time to time, but if he can be the inspiration of a team he is not the shaper of one. His football brain does not work in that way. Liverpool's most urgent need is someone in the image of Xabi Alonso, a driver, a tough obsessive, and no doubt Dalglish is more aware of this than anyone.
Meanwhile, Ferguson and Dalglish, the odd but compelling Scottish couple, will do what they can. But then you wouldn't want a whole lot more on any football high noon.
Cricket is missing a golden chance offered by Ireland
How ironic that the World Cup, the apex of one-day cricket but still mostly a miserably meandering version of the game we saw in all its glory Down Under during the Ashes series, should now be so intent on stripping away its best chance of redeeming glory.
You might have thought Kevin O'Brien's record-shattering century and the Irish victory over England would have at least a created a little pause for thought. But, no, apparently not; the pyjama game will be restricted to the Test-playing nations in future, and O'Brien wonders what that will do for the game in countries like his own and the Netherlands and Canada.
Nothing, of course. Which is sad when you think of the crowd-pleasing possibilities of a warm-up knockout tournament designed to glean the best candidates to walk in the footsteps of the legendary man from the Dublin Railway Union club.
Keegan still counts the cost of a lack of English players
Kevin Keegan gave up the England job with a sigh and a tear – but not before filing away one inherent difficulty.
This week he recalled it rather drolly, while still recommending that Spurs manager Harry Redknapp take the plunge if he is given the chance.
"When I was England boss I went to watch Arsenal against Chelsea," said Keegan, "and sat next to the French manager. He had 14 players on the field and I had one. Now that might not have been such a bad thing if I could have gone to Paris the next day and seen a game in which I had 14 on the field and he had one. Of course, it doesn't work like that."
You're right, Kevin, it's almost funny.