But injury can intervene, as it did to Carter before the final test in Hamilton and to Cruden after just 24 minutes of that 60-0 rout against Ireland.
Does anyone remember Colin Slade?
Late last year he was a 10-test All Black, the man primed to step up when Carter fell over at the World Cup.
Slade was a goalkicking five-eighths who operated with a wider viewfinder than others and had a calm tactical purpose.
Then he was injured and out of the tournament, a torn adductor adding to his heinous injury list of two broken jaws. That ill-fortune multiplied when Slade broke his left leg in his March return to the Super 15. With Carter also out of commission then and uncertain about his return, applications were being called for the vacant post.
Now Cruden and Barrett have skipped up a level after their starring job-share roles in Hamilton.
Then there is Tom Taylor with the Crusaders or Lima Sopoaga, although he has also run into injury with the Highlanders. It is a rich field of promise.
Barrett's enforced debut delighted backs coach Ian Foster.
"I think he'd be proud of it. He impressed us in the last two-and-a-half weeks. He's calm, kicked well, read the backfield well and brings a backline on to the ball well."
Barrett is the youngest of the All Black five-eighths, the 21-year-old son of Kevin Barrett who was a lock-flanker for Taranaki and the Hurricanes.
The five-eighths reckons he is one of the runts in the Barrett litter of eight - five boys and three girls - but he stands 1.87m and weighs about 94kg. He has an easy manner about his play and his conversation.
Initially he thought he would have to replace a damaged Israel Dagg before he was summoned to deputise for Cruden whose Achilles tendon troubles flared again.
"It helped that we were up by 20-odd points early on and that made my job easier," Barrett said.
"Aaron [Smith] played very well and we had a very good performance from the forwards and that made the job a lot easier."
The pace of the test seemed comparable to Super 15. The All Black forwards had the edge, especially at the breakdown, and once they got into their work they were relentless.
"I did not have time to have nerves. I was more nervous on Tuesday when I found out Dan had done his hammy than I was today. I dunno why, I slept okay."
Barrett reckoned the genes from his mum Robyn Sinclair's side of the family delivered his skills, while the Barretts brought the size.
"Mum's done a very good job. When dad was travelling playing rugby she was the one milking cows and looking after us. I can't speak highly enough of her," he said.
The five-eighths, who reckoned he never asked the origins of his Christian name but liked its uniqueness, bought 16 test tickets for family and friends, although about 30 turned up.
Earlier in the week Hansen had suggested if the test flew by then players were not doing enough work, so the five-eighths made sure he got amongst his duties.
Barrett looked ultra calm and lauded the experienced players in the side but admitted his thoughts were on fire.
It had been great to latch on to Aaron Smith's passing game. While injured Hurricanes halfback TJ Perenara had a strong clearance, "'Nugget's' pass is crisp".
Sam Cane
As Sam Cane buzzed around Waikato Stadium, the glow in the coaches' box grew brighter.
The search for a serious deputy to Richie McCaw has been an issue for about a decade, but Cane looked to be marking his card for that work.
Coach Steve Hansen was in little doubt later as he fronted to discuss the series clean sweep which ended with a 60-0 thumping of a feeble Ireland.
Cane picked up two tries and made a huge contribution in a superb team display.
"He was outstanding," Hansen said.
"What he has done is given me an easier night's sleep and now I know how I can look after me mate beside me here," the coach said nodding at McCaw.
"He is the best No 7 in the world, and now we have someone that might allow us to make sure he is around for a lot longer."
Tyro loosie Cane topped the tackle count and most watchers' player-of-the-day award. He deflected the post-match praise as he lauded the work of his teammates and Chiefs buddies.
"It comes down to the basics for quick ball.
"The tight five dominated set piece and from there Sonny [Bill Williams] gets over the gain line and the backs do their job," Cane said.
"That makes it easier for loose forwards to come in and do their job; they don't really want to compete when we have reached gain line and we can line them up and take them out early."
Playing strongly for the All Blacks would be a lift for renewed work with the Chiefs.
"It will be, no worries mate. I love the Chiefs and we have certainly got our eye on the title, so we will be working hard to make sure we get there."
Ireland had been a physical side whose ball-carriers ran hard and straight, and they hit the rucks with gusto. It had been a tough battle and he would be sore for a few days.
His work was a balance and one that did not work without the ball-carriers, support men and players who got the ball to space.
"If you run the right lines and get yourself in the right position, more often than not they will get you the ball. That is what I was trying to do," he said.
Had he told Hansen he wanted to start the next test? "Nah, not yet. I'll try and let my performance show him what I can bring to the side. We'll let him make the decision from there."
Aaron Cruden
How damaged is Aaron Cruden?
The answer will become clearer in the next few days as the first five-eighths tests whether his Achilles tendons will handle Friday's Super 15 match with the Highlanders.
He had not given up on that game, even though he was forced out of Saturday's test against Ireland after 24 minutes. Cruden has battled the problem since last year and never quite knows when the pain will return.
His left tendon had settled but his right Achilles started to trouble him soon after the international started.
"The next two days will be pretty crucial to see if I can jump on the plane and head down to Dunedin," he said. "I have tried to keep on top of it but they just seem to keep popping up at the worst times which is frustrating. You just have to do things to keep managing it, I suppose.
"It was fine in the warmup, everything else felt fine but then 10 minutes into the test, a slight change of angle and it sort of flared up again and got progressively worse as I went on.
"I was hoping to come out again after the bloodbin but the doc had a word and told me it would be best to rest up and get a bit of ice on it."
Cruden has not had any further issues with the right knee he hurt in last year's World Cup final against France, although he still guards it with some heavy strapping. He was bemused and frustrated about his Achilles issues.
"I dunno, something happened tonight. I woke up early. I was excited like a kid and could not wait for the game."
How did he explain his array of moves and back-of-the-hand flick passes? Were they a trickle-down result of playing alongside Sonny Bill Williams at the Chiefs?
"Sonny's been doing it for a while now, but other players have as well," Cruden said.
"It is just about winning the collision and getting good go-forward. Then you can flick it out the back of the hand and that's always handy to keep the movement flowing. We were able to throw a few tonight and they came off and that's great."
The All Blacks focused on pushing their support players past the Irish defensive screens and supporting with strong running lines and accurate passes.
"It was exciting to run around with a team with that talent. Tonight things stuck, but other times they might not," Cruden said.
