After Ireland returned from Twickenham with an historic Grand Slam for war booty, the provinces were left with one of the most challenging turnarounds in sport, with players having to decompress from the achievement of a lifetime and nine weeks cooped up in camp and then refocus for the most decisive period of the club season.

Everyone had the Monday off, the morning after the night before, when they’d enjoyed a great night in the Shelbourne and other spots around Dublin town.

On the Tuesday, all the Leinster players were back in for meetings, just to get back into club mode and learn a bit about their Champions Cup quarter-finalists Saracens that they’d be playing only 11 days later.

On the Wednesday, they were all off again, and most of the starters from Twickenham would remain off until the beginning of the following week. Carbery though was back in with Leinster on the Thursday, chomping for a start at last against the Ospreys in the Pro14 at the weekend.

He’d eventually take his short break a couple of days after coming on for the last 13 minutes of his province’s terrific win over Saracens in the Aviva, flying out to Dubai with his girlfriend. Their first day there, they met up and went for dinner with a couple of friends already out there: Jonathon and Laura Sexton.

It can often be a complex and tense relationship, two players vying for the same spot and jersey. Donncha O’Callaghan has spoken about how Mick Galwey didn’t exactly offer him a leg up when he was starting out. Peter Clohessy saved all his advice for Marcus Horan until he had retired. Sexton himself observed how in his first year or two with Ireland, Ronan O’Gara “wasn’t passing on any tips or anything like that”.

No such guardedness or awkwardness informs or pollutes the Sexton-Carbery dynamic. They’re less rivals, more colleagues, collaborators, friends.

“We spend so much time together. We actually get on really, really well,” says Carbery in his amiable, level-headed way. "I feel like if I had a problem or needed a question answered, be it rugby or life-related, I could go and ask him.”

Has he? Well, when it come to matters rugby, he has, yeah.

I know when I ask him something, he’ll give me an honest answer. He won’t beat around the bush or just tell me something I wanted to hear. I really respect that about him, because, sometimes, if you’re doing something wrong, people can be afraid to say something to you and then you just keep repeating that something that’s wrong, whereas with Johnny, he’d be more than happy to point you the right way.

A case in point: The only game in this season’s Six Nations that Carbery didn’t come on for Sexton was the opening game in Paris, when Sexton stayed on to produce probably the greatest clutch play in the history of the competition, but in the lead-up he had Carbery primed to kick the winning score, if necessary.

“We were in the [Stade de France] for a kicking session beforehand and there was a bit of a wind coming in at a certain direction,” recalls Carbery. “It was kind of swirling and I couldn’t get it, but Johnny stepped in, ‘look, it’s going to move right to left’ and after that I got it.

“Even just the small chats we’d have about foot placement or whatever, it’s a healthy environment to be in and, hopefully, the competition is driving him on as well.”

There’s a bit of fun and an edge to that competition. As well as Carbery gets on with Rob Kearney, who once colourfully admitted Carbery’s capacity to also play the full-back position was “giving him the shits”, his relationship with Sexton is closer for all the time they spend doing extras together, particularly kicking.

Over the Six Nations, while under the supervision of kicking coach Richie Murphy and joined for company by Conor Murray, they came up with an innovative way of inducing some pressure and adding a consequence to their goal-kicking competitions: Loser buys coffee.

More often than not, Carbery has quipped, coffee was on Murray. Sometimes, it was Sexton. Either way, it paid off and Sexton has enjoyed the benefits of paying up.

In Twickenham, Carbery entered the fray as early as the 34th minute, when Sexton suffered a blood injury before resuming his position for the start of the second half.

On the stroke of half-time, Carbery nailed a touchline conversion after Jacob Stockdale’s remarkable corner try, but the former Munster centre James Downey was just as impressed by Sexton’s reaction, noting that as the players trotted off towards the dressing room, Sexton waited on the sideline, letting other teammates file pass, until Carbery came over.

“He [Sexton] high-fived him [Carbery], patted him on the back of the head and the two of them ran off in together.”

For Downey, that interaction confirmed and personified the closeness of the squad and especially that tandem and why they made the best number-10 tag team in the competition.

On the same broadcast, former Leinster back-row Kevin McLaughlin claimed that Sexton’s influence on his understudy was “immense” and Carbery himself echoes that sentiment.

Although numerous commentators, such as Eddie O’Sullivan and Tony Ward have suggested he should leave Leinster to enhance his prospects with Ireland and Ireland’s prospects with him, Carbery reckons he’s better off staying where he is. If Sexton is the best out-half in the world, isn’t he possibly getting the best apprenticeship in the world?

“I’m quite ambitious and, at some stage, I want to be the number one for both Leinster and Ireland, but I know at this moment I have two world-class players in front of me in the two positions. I’m quite impatient, but I’m not impatient about this.

"I know the time will come when I get the opportunity to be [first choice], whereas if I become impatient, thinking the world is against me, that will impact on the way I look at things and I won’t improve as a player. I’m looking at it moreso that I can take bits of their games and apply them to mine and that will make me a better player and, hopefully, a starter.”

Although they’ve never spoken about it, Carbery is mindful of how Sexton himself had to bide his time under another inspirational out-half. Sexton was 23 when he burst on to the big stage, memorably coming on against Munster in that seismic 2009 Heineken Cup semi-final for Felipe Contepomi, someone Sexton has rated as along with Brian O’Driscoll and Isa Nacewa the best player he’s ever played with.

At the time, Sexton wasn’t on a central contract with the IRFU and essentially only third-choice out-half with Leinster, behind Contepomi and Nacewa, and similarly positioned on the grid with Ireland, behind O’Gara and Paddy Wallace. Carbery’s still only 22, second behind only Sexton for both province and country.

Sexton and Kearney are both 32, the same age Contepomi was when he passed the baton to Sexton. Unlike Contepomi, who had signed to play for Toulon the following season, Sexton and Kearney aren’t going anywhere anytime soon, but since they can’t play forever, either, Carbery doesn’t see himself going anywhere else too.

It’s not out of any fear of upheaval. Throughout his life, Carbery has routinely had to leave his comfort zone and head for somewhere new and challenging.

He grew up in New Zealand, the homeland of his father Joe, where in the mornings he’d surf on the beach next to their house before playing rugby at and after school. When the family moved to his mother’s hometown of Athy, an 11-year-old Carbery was shocked at the sight of everyone on his school bus wearing shoes and socks.

He’d settle in though and, guided and coached by Joe Snr, he’d help the local club reach the top division of Leinster underage rugby for the first time in its history, reaching a remarkable five out of a possible seven finals along the way.

For his Leaving Cert year, he transferred to Blackrock College on the recommendation of his Leinster U19 coach Wayne Mitchell. That was another culture shock, going from a small, co-ed school to a boarding, boys-only institution, where there were 200 students all in the one year, while the rugby was also an education.

“We were training every day, going to the gym before school and at lunchtime, lifting. With the Leinster youths and development squads on the way up, we’d have done bits of training here and there, but Blackrock definitely opened my eyes as to how much goes into being a top rugby player.”

Again, he thrived in a new environment — and position, lining out for the first time at full back — as Blackrock went on to defeat Clongowes in that year’s Leinster schools final at a hopping Donnybrook.

UCD wasn’t quite as smooth a transition; it just didn’t feel as close-knit as other set ups he’d been involved with, while Ross Byrne was ahead of him in the pecking order. The following season, Carbery transferred to Clontarf and instantly felt more at home. At the time, he still wasn’t able to drive, but coaches Andy Wood and Simon Broughton, both fellow Kiwis, would give him a lift across the city anytime teammate and Irish sevens international Mick McGrath couldn’t.

“It was a really welcoming club. They were always asking if I was okay with everything, did I need a hand with anything. With Clontarf, I felt like I was back playing with Athy.”

Under Wood and Broughton, he was given licence to take risks and conjure up magic, similar to how his dad coached him back home with the club, and both parties duly benefitted, Clontarf winning the AIL and Carbery winning man-of-the-match in both the semi-final and final. Six months later, he was in Chicago, his first day in green coinciding with the first day any group of men in green defeated the All Blacks.

Yet, while that call-up was obviously a quantum leap in his development, Carbery believes the past Six Nations campaign represented a similar spike on any graph reading of his understanding of the international game.

“Nine weeks in camp, it’s quite draining, both physically and mentally, so at the end of it, I was quite tired, but I felt I had learned and experienced so much from being exposed to that intensity and that pressure, that it’ll be invaluable to me.”

For most of his career, Carbery hasn’t just been a starter, but a firestarter, someone to ignite a match, build up a lead. In the Six Nations, he was a closer, there to see out a match, hold onto a lead. It was quite a shift in job description and mindset.

“Normally, I would always think about how can we break down a defence, go on the attack? but when you come on with 10, 15 minutes left and we’re already in the lead, we don’t need to chase it. It’s more about being able to squeeze the opposition than always just being on the attack.

"Put the pressure back on them, take it off us, whether that’s a kick into the corner or slowing down the rucks. So, I feel like I’ve gotten better at that, even by just watching the likes of Johnny in how well he does that, and then going out and doing it myself.”

What made that easier to do in Twickenham and the Aviva was that they’d simulate those conditions and scenarios during the week in Carton House. Joe Schmidt is renowned for drawing up and repping set-pieces — such as Tadhg Furlong’s stunning offload to Bundee Aki for CJ Stander’s try in Twickenham — but since the agonising failure to close out New Zealand in the Aviva in 2013, the Irish coach has tried to replicate the chaos of the final stages of a game just as meticulously.

“It’s the same in Leinster with Stuart [Lancaster]; he and Joe will normally chuck in at the end of training a scenario: ‘Right, you’re down by four points with three minutes to go, there’s a lineout, what are you going to do, how are you going to close it out?’”

Sometimes, the mayhem can begin a lot earlier for a sub like Carbery; a few minutes after Stander’s try, Carbery was in as a blood sub for Sexton. Again, though, they’d simulated that in training.

“In Carton, Joe might tap you on the shoulder after a few plays: ‘Look, jump in there [with the starters], run a few plays.’ Other times, it might not be until the very end that you jump in and you’ll be with other subs as well, but the odd time he’ll do it early on. Joe likes to use the phrase ‘starting on the bench’, because you could be on after just a couple of minutes, like Andrew Porter was against Italy.

"He came in for Tadhg and played incredible, because he knew his detail and was ready to fit in at any time. It’s about putting pressure on yourself to know every call and that if you’re chucked in, you’re able to execute, because you’ve rehearsed it beforehand in your head and in training.”

Most of the time in Carton, though, Carbery’s role was to run the second unit. Schmidt has another phrase: Collaborative competition. To beat an England or Wales on a Saturday, he needs Carbery and the second starting 15 to play in midweek, like England or Wales will at the weekend.

Carbery takes pride in how he trains during the week, so a Sexton as well as himself is ready for whatever happens at the weekend. As Schmidt tells them, the only way they should know that it’s just practice is by what they’re wearing.

“Our job is to put the starting team under as much pressure as possible. The other team isn’t going to make it easy for the starting 15, so we always feel in ourselves that we have to be better than whatever they face at the weekend. We might play a few of the plays which we’ve scouted that they do, and we feel that if we can do them better than how even the opposition might and break them [the starting 15] a few times in training, then they’ll be able to adapt for the game itself.”

Such diligence requires intensity, which is why Carbery likes to just chill when he is away from rugby. He reads quite a bit of fiction – though never on tablet, always in hardback or paperback – while as he shares a house with teammates Luke McGrath and Adam Byrne, he’ll often join them in watching Netflix; The Sinner is a current favourite.

Being sportsmen, they’ll naturally flick over to the cable sports channels too, regularly taking in golf, NFL and NBA. Ask him what sportsperson he admires and Russell Westbrook of the Oklahoma City Thunder is first off his tongue.

“I love his energy, the way he can create something from anything and the way he imposes himself on the court and expresses him off it; he’s always quite entertaining to look at.”

It’s easy to see why a Carbery is drawn to a figure like Westbrook, though modesty will stop short of walking into a stadium wearing a slim-fitting blue suit with no shirt. He too is fiercely creative and competitive, just like a certain other out-half at his club.

The most improved player in the NBA this season is the Indiana Pacers’ Victor Oladipo, who credits much of his transformation to playing alongside Westbrook last season in Oklahoma. Rather than stymie his progress, Westbrook inspired it. By learning from the best, the apprentice has become one of the best.

Whether Carbery also needs to eventually to step out from under the wing and shadow of his great mentor and take flight, none of us know. The past couple of weekends he was back as a starter, getting some badly-needed minutes in the Pro14 at both 10 and 15 after losing out on two months of action after breaking his arm during the autumn international win over Fiji, but today he’s back starting on the bench.

What we do know is that he’ll be ready to come in, having this week helped Sexton, his competitive collaborator, get ready.

Joey Carbery has teamed up with Avonmore Protein Milk for its new campaign ‘You’ve Got This’ which is showcasing what it takes to make it in high-performance sport.