THE margins could hardly be finer. Four years' work could be gone in an instant of humiliation.
Or the era continues, possibly for eight months into the spotlight of a World Cup.
Ange Postecoglou stands at a fork in the road, really for the first time since becoming coach of Australia in 2013.
For the first time since succeeding Holger Osieck 48 months ago, he faces a game where the result defines his future.
Win, or even draw 0-0, and the Socceroos go through to a final playoff for a place at the World Cup. Lose, and the Postecoglou era is done.
For the first time since 2002 there would be no Australian team at the World Cup. What a cruel epitaph that would be.
Every game of his until now has been sure of a sequel, but Postecoglou's contract runs until his team's interest in the World Cup is over, whether that's tomorrow, next month or next June. His service to his country has been lengthy with various teams.
"I've coached my country now for 11 years, I've coached my country more than I have club football," he says.
Much has been achieved, from becoming Asian champions to exposing a range of young Australian talent to the rigours and demands of international football.
Yet history would be cruel to the coach who failed to qualify for this World Cup, after attendance at the last three has rather got supporters used to the idea.
His pride in holding the role remains undiminished, fiercely proud of being the guardian of the current generation of players.
"I don't take it for granted that I'm coaching my country," he says. I don't know in terms of coaching if there's a greater honour to bestow upon someone, than to coach your own country.
"Every time we play it's a great honour. I don't take it for granted. When you play at home there's always a buzz."
Postecoglou talks with the note of exasperation that has grown over the past two years, as if he still feels misunderstood or bemused that people are still surprised by the certainty of his belief in his mission.
"There's always that possibility every game, that I could be gone," he says.
"I don't think that way, mate. That kind of stuff doesn't really enter my thinking. I've never taken it for granted and I certainly don't think about myself in this situation, whether it's the first or last game.
"I've been pretty big on preaching to the players to treat every game like it is your last and that way you appreciate every one of them.
"If Tuesday is it for me then I won't go into it with any different feeling than I have any other game.
"We'd much rather be already heading to the World Cup, but it's not a bad alternative (in the sense that) if we didn't have these games we'd just be having friendly games and it would have been hard for us to get any major games.
"We'll still get enormous games in this scenario out of the next three games.
"For this group of players, if they come through this then belief just grows in themselves and what we're doing, and that will hold us in good stead going forward."
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