WITHOUT Michael Cheika's influence on Irish rugby, and Leinster rugby in particular, we may never have heard of Joe Schmidt in this part of the world.
Schmidt's undoubted qualities may inevitably have surfaced elsewhere - as is now generally acknowledged, his expertise has already marked him down as someone who will tread a similar path to Cheika's - from provincial rugby to national coach of his native country.
But Schmidt's opportunity might never have happened were it not for the seminal groundwork laid down by the then unheralded Cheika, who pitched up in Dublin nine years ago as a novice coach, unheard of in this part of the world.
Schmidt may have broken new ground in the sport here but Cheika planted the seeds as the two former Leinster coaches, now both at the peak of their profession, collide just a few miles from provincial HQ this Saturday.
It is always tricky to apply the theory of 'Sliding Doors' to sport but, in this instance, there is merit in the argument; a brief recall of the circumstances in which Cheika was recruited solidifies the argument.
One could even just start and finish the debate by positing the then status of Brian O'Driscoll; a player thoroughly disillusioned at the prospect of remaining at a perennially under-achieving side, now greeting their fourth new coach in as many years.
Having none too subtly raised his metaphorical hemline in the direction of Biarritz, O'Driscoll met with Cheika and outlined his manifold frustrations and his desire to cast aside years of individual and collective failure with Leinster.
"Let's get down to work," Cheika told him. They did so - and never turned back.
It was a mountainous task - literally. Cheika ran the side - hard - up and down Killiney Hill. Some players could take it. The weaker ones, who couldn't, were eventually cast aside.
He has done the same at the Sydney franchise, the Waratahs, who overcame similar obstacles to become Super Rugby champions this year. "It's symbolic," says Cheika. "We're prepared to run 10 metres to gain 20 centimetres at the other end if that's what it takes."
The scale of the task - both on and off the field - had been hammered home in his first season, when Munster snaffled the majority of the tickets for a seminal Heineken Cup semi-final in Lansdowne Road and destroyed their opponents on the pitch too.
A symbolic swansong would arrive in Croke Park en route to the definitive breakthrough for Leinster when a world record attendance for a club game would witness his side turn comprehensively turn the tables on Munster in a semi-final three years later.
Cheika, in congress with a supportive chief executive and a hungry cadre of players, had wrought an extraordinary transformation in culture on and off the field that would see them ascend to the top table of European rugby.
The squad that won the Heineken Cup housed just nine survivors from his initial squad of 36 players, the side had moved from Donnybrook (a crowd of just 1,700 watched one of his early games in charge) to regularly fill the RDS and, occasionally, the Aviva; instead of operating from portacabins, the squad now boasted world-class training facilities.
A self-made millionaire thanks to his fashion business - he has always said he is not a career coach despite fashioning a more than decent career from being a coach - this Sydney man more renowned for couture transformed the culture in Leinster rugby.
"I just wanted to make sure that I could leave a legacy so that when I go back to watch them in a few years' time, I can sit in the stand and be proud, knowing that I was part of building that, you know?," he told me recently.
"Because that was the plan. That's why it was important to pick the right time to leave. If I hadn't done what I wanted to do in those five years, well, I wouldn't have deserved to stay on in the first place.
"But ultimately, as Joe Schmidt will admit, none of it is possible without a good player group. And the players in Leinster have just been top notch."
Cheika rid Leinster of the cosy consensus wherein the under-achieving players had, often due to poor leadership, lost their way. Ultimately, he allowed them to become more responsibly player-led - but only after he had forcibly altered the culture.
None of the Leinster pack survived his first ever Magners League match in charge - characters such as Rocky Elsom, CJ van der Linde, Bernard Jackman, Ollie le Roux and Stan Wright reflected Cheika's canny knack of identifying character.
The most important catalyst for change was the repatriation of title-winning Leicester duo Leo Cullen and Shane Jennings, both of whom had left Leinster precisely because the club had lacked direction and focus.
Cullen would develop into European rugby's most successful captain of all time, lifting the trophy three times and ensuring Cheika's legacy survived, and thrived, as Schmidt empowered the group to transcend his predecessor's seminal influence.
Cheika suffered no fools; even the brilliant but barmy David Knox was eventually excised when he and forwards coach Mike Brewer could no longer communicate.
Gordon D'Arcy was publicly upbraided for wearing flip-flops and a psychedelic t-shirt to a media briefing and ordered to wear Leinster kit; Shane Horgan was dropped for missing training during the Six Nations despite being an Irish regular.
The senior players had run the show before Cheika's arrival; now he was in charge. Their respect would be reciprocated when their responsibilities soared.
"In the past, Leinster players did what they were told," said Cheika. "They were not given their head to coach themselves. I want that to happen."
The youngest child of Lebanese immigrants, Cheika grew up in a working-class suburb near the famous Randwick club; his environment framed a character that is tough and unyielding, but also sympathetic and gregarious.
While he failed at Stade Francais - they were a financial mess, which didn't help - he was described as "an inspirational leader and an agent of change" when doing with his local side the Waratahs what he had done with Leinster.
As with the Waratahs, he has now banned mobiles at team dinners, headphones in the dressing-room ("Cydni Lauper ain't going to win you games," he told his nonplussed players); there is no walking between drills.
In Sydney, he addressed supporters' concerns; brought thrilling rugby back, the crowds returned and so did the silverware. Now he seeks to repeat the task.
When predecessor Ewen McKenzie's difficulty became Cheika's opportunity last month, the 47-year-old hesitated; he knew the value of his experience and he ensured his salary was upped at least 20 pc - he could earn some €800,000 next year alone.
Few would bet against them staging an audacious World Cup ambush, buoyed by a new coach and united again as Kurtley Beale returns to the fray; Cheika also wants all Australian franchises to have an input into the team, something he learned from his time in Ireland.
There won't be any repeat of last year's drinking session in Dublin; Cheika trains them so hard the players are too exhausted to go out at night. And don't expect him to indulge the hapless ARU jersey-huggers either.
Cheika will do things his way. He knows how to put the smile back on a team's face. But he will do so with an iron fist inside his velvet glove. Nobody does tough love better.