Zero hour for Gordon Strachan and Alex McLeish arrives at 12.30pm, when the cauldron of Ibrox will be filled to capacity for the season's first Old Firm derby.
"When I took the job [as Celtic manager] I thought I had an idea of the magnitude, but the reality was mind-blowing," Strachan said yesterday. "I'm guessing the same will apply [to this game]."
Never before have former team-mates managed against each other in a Rangers-Celtic match, and if Strachan or McLeish think there is some middle ground available to them - enemies for 90 minutes, mates afterwards - then they are out of kilter with the rest of Glasgow.
Acne cream, rollockings, domestic trophies, European glory and two World Cups. From boys to men, wannabes to winners, Strachan, 48, and McLeish, 46, shared them all as players, first with Aberdeen under Alex Ferguson and then with Scotland.
In management their paths diverged, Strachan with strugglers Coventry and Southampton before taking a plunge into the deep end at Celtic. McLeish stayed closer to home, making challengers of Motherwell and Hibs before being lured to Rangers in 2001.
Distance did nothing to dissipate a 28-year friendship. Now, for all their protestations to the contrary, proximity surely will. Either that or one of them will not be in a job long enough for it to happen.
Because just as their 1980s mission at Pittodrie was to break the Old Firm duopoly, now, as Glasgow's Godfathers, the aim is to break each other. It is what the fans demand.
"In my naïvety, I thought we'd be socialising a lot when I moved here, but we haven't yet, not once," Strachan said. He added that time constraints were the main factor, but acknowledged that their jobs will introduce a new dynamic to their relationship. "Someone has to lose [in the battle for Old Firm supremacy] and how to handle that could be difficult."
Ferguson has said: "I have been in San Siro for the Milan derby, in Barcelona for the visit of Real Madrid, I have seen Benfica-Porto and all the big games in England and, believe me, there is nothing, just nothing, to compare with the atmosphere of Rangers-Celtic."
Strachan versus McLeish puts the knobs on, not just because these Ferguson protégés are facing each other as managers for the first time.
Ferguson has always been more of a mentor to "Big Eck" McLeish, a fellow Glaswegian and his one-time centre-half colossus, than to Strachan, the Edinburgh "wee man" who could dazzle in midfield but about whom he sniped acidly in his autobiography: "This man could not be trusted an inch ... I would not want to expose my back to him in a hurry."
McLeish has arguably been the more Ferguson-esque as a boss: tough, sometimes aloof, big on discipline, a builder of sides founded on strength at the back.
Strachan has tended to be wittier, cheekier, more inclined to put an arm round the shoulder and ask his men to play for the badge than rage in their faces. Also - and this is meant positively - he is more of a dreamer, a manager who you sense would take no greater delight than moulding a tricksy, entertainment-driven side if only the pesky matter of needing results was not such a priority.
His desire to provide an outlet for creativity is embodied by Shunshuke Nakamura, his Japanese playmaker, one of several foreigners on each side likely to have a baptism of fire in their first Old Firm matches today. They will emerge as heroes or toast. This fixture does not deal in perspective.
Celtic's Craig Beattie, who scored twice for Scotland's Under-21s in midweek and who is expected to start up front in place of Poland's stuttering Maciej Zurawski, is another who could make giant leaps or land with a bump.
Events since the start of the season have only stoked the derby furnace, not least because SPL leaders Hearts have made such a wonderful start and can only benefit from the Old Firm obsessing about each other.
Glasgow lore says that Old Firm managers are only ever three hiccups from a crisis - and derbies count double - so Strachan's first two games, a European drubbing and a 4-4 draw at Motherwell, had him edging towards a precipice. Despite a steadied ship, doubts linger among the faithful.
If he masterminds the kind of derby debut that his predecessor Martin O'Neill did, a 6-2 win, four years and 51 weeks ago today, he could be set fair, as the Ulsterman was, on a voyage of achievement. A draw would be acceptable. But defeat? Cue a fresh debate about his credentials. Such is the harsh reality in a city where 100,000 people have Old Firm season tickets, and tens of thousands are parked on waiting lists.
McLeish has his own, lesser concerns. Lesser unless Rangers lose, that is. A first defeat to Aberdeen in seven years last weekend - when the influential Fernando Ricksen was sent off, was hiccup No 1 of the campaign. A draw today would be No 2. A loss would spell a crisis ahead of next week's Champions' League qualifier against Famagusta of Cyprus.
"This job is so exciting it's not true," Strachan insists. And he has yet to taste the biggest game of them all.Reuse content