The two years of “retirement” haven’t dimmed him. Indeed, they may have extended his career. Already established as Leinster’s greatest ever overseas signing, which is saying something when you think of Felipe Contepomi, Rocky Elstrom, Brad Thorn and all the rest, the second coming of Isa Nacewa is threatening to be almost as glittering as his first.

After his two-year sabbatical in retirement, last season Nacewa scored nine tries, his best haul in six campaigns with Leinster. This season there’s been 10 tries in 18 games, and, for the sixth campaign in a row he is set to play 20-plus games.

Granted, that first five-year stay from 2008 yielded a haul of three Heineken Cups and a Pro12/Challenge Cup. Despite topping the Pro12 table last season and reaching the final, a tame European pool exit after just one win in five games, was not what he had returned for.

“We judge ourselves on Europe, don’t we? But I think if we didn’t have last season we wouldn’t be in the position we are in now. That’s the beauty of an off-season. Take a short hard look at yourself; realise some honest truths and try and make change, and with a full off-season and pre-season, without a World Cup, you can do that.”

This season’s rejuvenation has energised him, as have the new young tyros around him and the “new perspective” provided by Stuart Lancaster. “It’a a fun place to work.”

At 34 he has maybe slowed down a tad. “A tad. A tad. But all the young guys have sped up I think.” But with age comes wisdom. He can also read a game as well as anybody.

“I think you just get smarter as you get older,” he muses. “I’ve seen a lot of the pictures before. But the young guys are good, really good. I think back to 2008-09, when you had Fergus (McFadden), Eoin O’Malley, Rhys Ruddock, Dominic Ryan – like a wave from the academy came through. There hasn’t been another wave like that until now in my time here.”

“But where do you start now? Joey (Carbery), Locko (Rory O’Lloughlin), Adam Byrne, Peter Dooley, Ross Molony, Ross Byrne, Nick McCarthy. Chuck in Jamison Gibson-Park. All of a sudden there’s a new wave who deserve their time.”

Garry Ringrose is still only 21? “Robbie Henshaw is only 22,” Nacewa responds, wide-eyed. “He’s meant to be 26 in my eyes.” He goes through a potential back-line in which Gibson-Park, and the incoming James Lowe, would be the oldest at 24.

The only comparison Nacewa can draw in world rugby is the Canterbury Crusaders academy.

So is the current crop too young to win a European Cup like the golden era did on three occasions?

“No,” he says with that steely-eyed intent he reserves for one of his more definitive answers. He recalls how six of them made their first European start in last season’s win over Bath, and the progress made by players such as Ross Byrne, Luke McGrath and Ross Molony, while also noting how well Leinster now manage players such as Ross Molony.

“When I first got here you were having 21- and 22-year-olds getting double shoulder reconstructions. One thing they’ve learned over time is not to over expose them.”

Eleven players from the squad which beat Clermont in Bordeaux and Ulster in the 2012 final to earn that third star on the Leinster jersey have retired, and another, Ian Madigan, has moved on. That was a brilliant, mature side; Leinster’s best ever.

“Yea, it’s far different,” says Nacewa. “A different team in culture, a different time and different coaches.”

He cites the way Stuart Lancaster blooded and quickly developed young England internationals who are now high achievers, and is doing the same at Leinster.

Similarly though, where young players had Brian O’Driscoll, Brad Thorn, Leo Cullen, Shane Jennings, Gordon D’Arcy and others to look up to, so this generation have Johnny Sexton, Sean O’Brien, Jamie Heaslip and, though he wouldn’t say so, Nacewa himself.

“They’re very positive leaders, and in that respect Zane Kirchner has been outstanding, and how he’s helped to mentor some of the younger guys. And I think we looked at last season and we would have been stupid if we hadn’t learned from it. One of the things the leaders took on board was that we needed to help these young guys become better, and that’s what we’re about.”

When Nacewa retired at the end of the 2012-13 season and returned to Auckland, he anticipated taking a complete break from the game. But the Blues head coach, John Kirwan, invited Nacewa onto their backroom team as a mental skills coach, mentoring younger players, while also working alongside Graham Henry and Mick Byrne. How could he turn down the chance to work with such rugby royalty?

“But it was a different Blues environment from when I left, and so different from Leinster, and the Michael Cheika and Joe Schmidt campaigns, where I had won five trophies in five years. The Blues haven’t won (Super Rugby) since 2003.”

He had to stop comparing the two.

“I learned a lot in the first nine months and the second season was a lot easier. But still I kept fit.”

Being part of the coaching staff also meant training with Jason Price, the Blues’ S&C head coach. “You can’t beat him in any exercise possible. He’s just a fitness freak. We did a lot of circuit based, body weight stuff and a bit of running on the side, and played squash.”

Having decided to return to Leinster in 2015, Price put Nacewa on a three-month training programme which he describes as “hell for leather”, and adds: “I pretty much had a personal trainer in the whole lead-up to coming back here. I owe Jason Price a lot. He whipped me into shape, wrote my programmes and he’s a real good mate, and we keep in touch. I owe a hell of a lot to Pricey.”

The return to Leinster happened in part by chance. “It was a few strange text messages either way, between me and Shane Jennings, or Leo, and then Matt O’Connor, and the next thing I was on the phone having a conversation with Matt with the thought of coming back here.”

“And it wasn’t a hard decision to make, even for my wife Simone. Mia and Ellie had just started school. Lucie was still at ‘kindy’, day care. The thought of coming back to Dublin excited us both. We knew the colour of the grass on the other side of the fence. Coming back through the port tunnel, we just started living in Dublin again. The transition was seamless. Nearly two years on from arriving back here it felt like we never left.”

All four girls have been born in Dublin, after Laura (six months) arrived on September 28th – a sister to the twins, Mia and Ellie (seven and a half) and Lucie (five and a half). The first three were born in Mount Carmel, Laura in Holles Street.

Nacewa is a Kiwi, of Fijian descent, but has become an adopted Irishman. “It’s the people first of all. It really is. We’ve never felt out of sorts here in Dublin.”

Now, as if to further prove the point, Nacewa is the Leinster captain.

“I love this place. I love Leinster. I love Dublin. It really is our home. It really is my home club. I’ve felt that way for a long time. It’s a huge honour to captain this place. I wouldn’t say it’s easy when you’re winning, but there’s a hell of a lot more challenges when things aren’t going right.”

“Last year alone, when Kev McLaughlin retired, and captaining Leinster for the first time, you learn a lot about yourself. You learn a lot about all the players and staff, and you’ve got to see the bigger picture. The number one priority is to play well but there’s a lot of other things and responsibilities. I learned a lot from being two years away from playing, and I’ve learned so much from Stuart in less than 12 months, on the field, off the field, mindset. It’s enjoyable being captain.”

He and Leinster have exercised the option of playing on for at least one more season. “I’m here to chase trophies and stars,” he says, in reference to the three existing stars on the Leinster jersey. “And we’re just happily enjoying life. Number one, our girls are happy, first and foremost. We’re finally starting to travel around Ireland.”

Last year they went to Sneem in Kerry. “Stunning. It blew my mind. I can’t believe it took us so long to get down there. We plan to go to the Connemara direction. You don’t need to be anywhere else in Europe when it’s hot. I was blown away by how beautiful south-west Kerry was, and now I just can’t wait to see more.”

“You drive past Killarney National Park and drive over the hills to Kenmare, it’s very like the middle of the North Island. It’s bare and barren. I thought it would be a hell of a lot more commercialised, but it’s not. There’s endless coastline that hasn’t been touched. There’s a lot of New Zealand like that.”

Beyond playing, with all this exposure to the work of coaches, it’s given Nacewa a mind to try it himself one day. “It’s definitely on the radar. I didn’t think I would want to get back in but I’ve had Michael Cheika, Joe Schmidt, Pat Lam, Graham Henry, Stuart Lancaster. I’ve had some pretty good influence in my life, and those coaches have already shaped the way I’ve thought about rugby, and definitely shaped the way I’m putting my own coaching philosophy together.

“I do look at the game and really love it, and I would love to give something back in a coaching capacity. I enjoy studying coaches in the NFL and their philosophies too. I think learning from Stuart this year alone has helped me discover a bit of passion for it. I got a taste for it with the Blues and it’s definitely something I am looking forward to.”

One day. Not just yet though. Not just yet.