He has time to slip across the road from Eden Park for a coffee, where the "butcher's boy from Mangere" who failed School C orders a double expresso in an Italian accent. He's wearing dress-denim trousers, a pinstripe jacket and tie and the shiniest pointy patent leather shoes, made in Italy.
"This is how a typical Italian businessman would dress," he says. "I'm a butcher's boy from Mangere who lives in Venice and Tokyo. I still think about where I've come from and feel very privileged. It's sport that's given me everything and I feel very honoured that I can come back here and do this. People talk about the pressure but this is the greatest job."
The media flurry surrounding his appointment this week - ousting Pat Lam as the Blues' head coach - may seem out of proportion, given that most Auckland rugby fans long ago found better things to do than traipse to Eden Park to watch the Blues fumble and flop. But there's more than rugby at stake. With test cricket gone from the park in summer, the spectre of a stadium that had millions spent on it for the Rugby World Cup sitting empty in suburbia cannot linger.
Turning to Kirwan, whose coaching pedigree is with second-tier rugby nations Italy and Japan, may seem a bit of a punt by a franchise desperate to turn the clock back to the 1980s and early-1990s, when the young JK scored thrilling tries for Auckland and the All Blacks.
But Kirwan is quietly determined to be recognised here not for his past deeds but for his coaching abilities. Success, he knows, will not only bring the crowds back to Eden Park but could lead to even higher coaching honours - another step on a journey of considerable personal growth.
But failure - and there are many who believe the Blues' problems are insurmountable - could seriously damage the Kirwan legacy.
Kirwan's story is sporting folklore. An apprentice in his late father Pat's butcher shop, he was plucked from third grade into an emerging Auckland team by coach John Hart. With his Patrick Swayze locks and looks, blessed with power, pace and a sidestep that left opponents grasping at thin air, he was a stand-out in a team of rare talent. As Hart said of the 18-year-old, he had rare maturity and confidence without being over-confident - though, as he got older, the onfield aggression sometimes boiled over into petulance.
Auckland's team of champions powered an All Blacks' era of similar domination. These days, the franchise with the country's biggest player base (it covers Auckland, North Harbour and Northland) hardly rates a once-over from the national selectors.
Only later did we learn that his playing days were both the best and worst of times for Kirwan. His frank admissions about depression seemed to explain his less-endearing traits and caused even his detractors to admire his guts.
Coaching at international level for much of the past decade, he has continued with mental health promotion work and is credited with helping to break down the emotional stone wall that defines the Kiwi male psyche.
Last month he was knighted for his health work, though he struggles with being called "Sir John" (or even "Sir JK", as a passing bunch of academy players outside Eden Park learned this week. He barked at them to "work hard", rather like Hart used to).
Kirwan's mental health work has created another legacy: people think they know him through the television ads - and they judge him. Many assume he remains mentally fragile. So it was groaningly predictable that his appointment would inspire social media comments such as "Kirwan gets the blues" and wags in pubs and around watercoolers to portray him blubbing after every inexorable defeat. Such are the expectations of this franchise.
There's a serious side to the jokes. We need look only as far as his predecessor Lam, holding back tears before the cameras, to see the toll that media and fan-pressure can take. Plenty of Kirwan fans think he is making a mistake.
He feels for his old Marist and Auckland team-mate Lam, but seems confident he can handle the clobbering machine. People underestimate how tough he is, he says. He laughs heartily at the "blues" jibes - "That's just good Kiwi humour."
He talks of his depressive illness in past tense - a phase of his life that he learned from. But he also stresses the importance of maintaining "wellness". He knows the signs and has his coping strategies, which include surfing, exercise and an appetite, learned in Italy, for long lunches at home with friends, lingering over fine food and wine.
"I think wellness is everyday - I won't let [the pressure] mount up. I'm conscious of making sure I get the balance right."
He is a realist, telling The Observer not long after he was sacked as coach of Italy: "There are two types of coach, aren't there? Those that have been sacked and those waiting to be."
But why risk his reputation by taking on a franchise which many rugby heads believe is so dysfunctional it's beyond any coach to fix?
Kirwan says Fiorella was behind his decision to return.
After last year's World Cup, he decided to not seek reappointment with Japan and returned to Treviso to weigh up his options. One was to seek a coaching post with a rich European club. Instead, the family opted to come to Auckland.
"I was at a real crossroads. I'm very fortunate - I have a really fine life in Italy. I could have kicked back a bit, continued my TV work for Sky Italy and a bit of corporate work. I talked it over with my wife and she said: 'aren't you a bit too young to be doing that?' The alternative was to continue with my career and try to be the best coach I can be."
He says Fiorella and the children are excited about coming to Auckland. The city has come a long way in 10 years and is benefiting from waterfront redevelopment and its internationalisation.
"I think a big city like this deserves the Breakers and the Warriors and one of the best [rugby] franchises in the world that fills this stadium. We can only control that by winning football games and that will be a by-product of doing things well.
"Imagine this place like it was during the World Cup - buskers and balloons and the fans spilling out afterwards and into town ..."
He won't shrink from the limelight if things go wrong, he says, he'll continue to go out and enjoy what the city has to offer.
He says he's done his research and is going in with eyes wide open.
"Auckland is one of the most beautiful cities in the world but it's a tough city - if you're not good enough, it spits you out. You have to be resilient to be here, you have to front."
Rugby experts believe the reasons for the Blues' demise go well beyond the players and coach to the way the franchise has been managed. Kirwan won't be drawn on where any off-field problems lie - though he mentions more than once that much of the city's budding talent is hoovered up at age group level by rival franchises "who take them away and turn them into great rugby players".
Young talent is everywhere, he says, but talent doesn't make good professionals. "That's my job."
His focus is on what he can do to get the best out of his players. With forefinger and thumb, he makes a 2cm gap to show the difference between a winning and losing team.
"It's not about improving them mentally or physically or their work ethic - it's all those things. Where can I change things?"
He is a details man, he says. The head coach will oversee a wider training squad of around 42 players and a dozen or so staff. As Lam found, issues come up within the group that have little to do with rugby training. "If I'm not totally organised I won't be able to catch those balls."
The self-belief of old is behind his vision but he is playing down expectations of an overnight return to the glory days.
This team, he says, is 18 months away from fulfilling its potential - "like the difference between a 1996 Amarone [the full-bodied Italian red] and a 1994. The '96 may be cheaper, and it's still good, but it's not as good as the '94."
