The All Blacks had arrived, and it was the start of a long century for the rest of the world.
When Duncan started coaching at Otago Boys' High School after World War I, an era of perpetual tactical innovation was dawning in Otago rugby.
It would shape rugby far beyond the province, and irreversibly change the relationship between players and their coaches.
In Jimmy Duncan's 1st XV was "Young Vic" Cavanagh, whose father "Old Vic", as coach of the University club, had devised a system whereby small forwards could compete with bigger ones at the breakdown by binding together and attacking the space beyond the ball.
What we now know as rucking quickly became central to the Otago game.
When Young Vic's career as a player ended prematurely, he took what he had learned from his father, added the appreciation of time and space passed on to him at Otago Boys' by Duncan, fused it with psychological insight and communication skills that were all his own, and became one of the greatest coaches in New Zealand rugby history.
Perhaps the most fondly remembered of all of those who studied under Jimmy Duncan at "The High School" is Charlie Saxton. A 1.65m halfback whose international career was curtailed by World War II, he was, with South Africa's Danie Craven, the outstanding early exponent of the dive pass.
His name is linked in history with that of the famous Springbok for another reason: the spoiling tactics of South Africa under Craven in the 1950s provoked the creation, by Saxton and his fellow administrators, of the Otago "code of ethics" in 1959. What we now call offside play was outlawed from the game years later, when the rest of the world caught up.
The rest of the world never did catch up when it came to the cult of the coach.
Jimmy Duncan was the forerunner of a New Zealand movement that legitimised rigorous thinking about the game, and 100 years later it's clear, from the number of his compatriots in top coaching jobs around the globe, that the standard continues to be set there.
Occasionally stories will filter back from overseas about players finding their hard-bitten Kiwi coaches too "headmasterly".
There's a good reason for that: most of them are former headmasters, and those who aren't are still products of a system founded on the teacher/pupil values of traditional boys' boarding schools such as Otago Boys' High.
Today the cinder-block walls of the Otago Boys 1st XV changing room are decorated by those who play in the team, and the artwork reflects the hip-hop culture that preoccupies many teenage rugby players.
The Cavanaghs may not have approved, but Ryan Martin, at 30 years old the youngest 1st XV coach in the history of the school, seems to know exactly what he's doing.
His grandfather, Herbert, played outside Charlie Saxton for Otago, and as the clock ticks down to one of the biggest games of the year, against local rivals King's High School, Martin says that in a traditional school some things don't change.
"I would say a quarter of our roll are here to play rugby, first and foremost. Our hostel is chock-a-block at the moment, with boys from the deep south, Queenstown, Wanaka, Oamaru, North Otago, 140 of them in there, the majority playing rugby."
Martin was captain of the Otago Boys' 1st XV which included Richie McCaw and drew the 1998 national secondary schools final with Rotorua Boys. He says there has been a power shift in South Island schools rugby since the establishment of the Press Cup in Canterbury 10 years ago.
"That competition has done wonders for the schools up there like St Bede's and Christchurch Boys. Our Highlanders comp was modelled on the Press Cup, but it's only in its third year and there's only three or four strong teams. We average 60 or 70 points a game."
There are other factors to consider.
"We've been behind the eight-ball in terms of recruiting. There was a quarter-page ad in the Otago Daily Times, placed by Christ's College up in Christchurch, willing to pay props to go to their school. In our paper. And St Bede's, who are the benchmark for the South Island at the moment, are very big recruiters, with a very big chequebook."
Despite this, Martin's first year in charge is going well, with dominance over Southland Boys and a stingy defensive record encouraging signs for the years ahead.
"The Otago union has only just realised it needs to start investing time in secondary schools rugby. There are so many players who've been lost because they've gone to other regions. But now the union is putting more time into it. There's going to be some good boys coming through in the next few years."
At Carisbrook the temperature is pretty much non-existent as hundreds of teenagers from Dunedin's two biggest boys' schools shuffle into the stadium, wearing the traditional South Island mid-winter uniform of shorts and maybe a blazer.
The floodlights come on, illuminating the light rain sweeping across the ground, and the game begins. Otago Boys' centre Michael Collins dominates the early stages, and there's a bit of Conrad Smith about the way he straightens and scores under the posts in the fifth minute.
King's are looking vulnerable until a counter-attack by their fullback Dan Fowler changes the whole tone of the match.
Receiving the ball in his 22, he steps three defenders and tears off on a 30m run upfield.
When he goes to ground his forwards pile in and don't stop piling in until halftime. At the break Otago Boys have a narrow lead that flatters them.
Teenagers being teenagers, the Otago Boys' players are 10 minutes into the second half before they remember to execute the instructions given to them by Ryan Martin at halftime.
When fiercely mulletted King's High winger Jayden "Chewbacca" Dovey allows a harmless looking kick to bounce into touch on his 10 metre line, it sparks something in the Otago Boys' forwards, and they go on a controlled rampage, stealing possession from the lineout and then hitting rucks and recycling with increasing momentum.
They wait until they are sure King's High are firmly in reverse, then finally release the ball to their three-quarters, who now have the width of the pitch to play with.
A short ball from Collins reaches second five-eighths Aleki Morris just as he's hitting top speed and he goes over for the try that extends his team's lead to nine points. King's fail to score again, and the final score is 43-22 to Otago Boys'.
Richie McCaw is finishing off an All Blacks media session when I arrive at Auckland's SkyCity convention centre. His morning's work is over, but he's keen to talk about his old school.
"I think traditional schools like Otago Boys' teach you how to be a leader. I was at the boarding hostel, and when you're there you learn to fend for yourself. That's certainly something to draw on when you become a captain and you need to back yourself a wee bit.
"I remember one morning Jeff Wilson came in to talk to us, and he said 'schoolboy rugby is some of the best rugby you'll play', and I thought 'how can you say that when you're playing for the All Blacks?'
"Looking back now, where we got to in that final year is something I'm still proud of.
The school has a tradition and the 1st XV is a big part of that. You feel part of that history when you're there."
Jimmy Duncan had a theory that the ideal wing-forward should be like a sheepdog, corralling and intimidating with his presence before striking instinctively when the opponent is most vulnerable. He never lived to see McCaw play - some men pay a price for being years ahead of their time.
