If you are in any doubt Rieko Ioane will recover his form, consider the remarkably parallel story of fellow All Blacks wing Joe Rokocoko.
Ioane's comeback showing against Canada was good, but not great; he probably didn't do enough to displace George Bridge (or Sevu Reece) from the All Blacks' top team.
Which means his All Blacks career is following an eerily similar course to Rokocoko. Like Ioane, he burst on to the scene as a youngster — famously playing for the All Blacks before playing for Auckland. Ioane was 19 when he made the All Blacks; Rokocoko had only been 20 for a week on his debut.
They are of almost identical dimensions — Rokocoko at 1.89m and 103kg; Ioane 1.89m and 104kg. Both had scorching pace, scoring test tries as if it was as easy as rolling over in bed. Rokocoko scored 27 in his first 23 tests; Ioane 24 in 27.
Both struck problems two years into their careers. Ioane's ordinary 2019 came after two stellar seasons. Rokocoko, debuting in 2003, lost confidence and form in 2005 — dropped for the Lions series that year, packed off to the national sevens team and Junior All Blacks.
It could have been the end — Rokocoko could have been a nova, a star whose brilliance quickly fades. Coach Sir Graham Henry said his form had dipped behind that of Doug Howlett, Sitiveni Sivivatu and Rico Gear. There were question marks about his ability under the high ball and suspicions his speed had tailed off; there are similar fears about Ioane's pace now.
Henry correctly predicted Rokocoko would play many more tests for New Zealand — 45 more, to be exact, scoring another 19 tries to be equal second (on 46, with Julian Savea and Christian Cullen) behind Howlett (49) on the All Blacks' test try-scoring ladder.
But he had to reinvent himself. Originally weighing about 99kg, he put on an extra 4kg and focused on focus. He had been guilty, he said, of overthinking options when the ball came to him. When you have that much weaponry, it's not surprising options can obstruct execution.
"I was maybe guilty of thinking about all the things I could do when it would be better for me to pick one thing and do it as well as I can," he said. "Just focus on one thing and then totally commit to it."
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The extra weight gave him confidence he had the explosive power to beat opponents on the outside, or to step off either foot, or run right over them: "I certainly feel comfortable running at this weight and as sharp as I ever have; I really wanted to become more explosive, like Rupeni Caucaunibuca and Sitiveni Sivivatu. When those guys step, they really blast off either foot and are hard to tackle."
Ioane might have to go through something similar to regain that extra bit of zip. He might not need more weight but could need similar help from All Black and Blues coaches to clear his head and grow his confidence. Rokocoko worked hard on his speed, something Ioane has also been addressing.
It's doubly difficult for wingers and fullbacks; their careers tend to take place in open spaces — where loss of gas is quickly remarked upon, never helpful to confidence.
Remember how quickly Julian Savea's form tanked — leading to a sudden exit from the All Blacks. Cullen was another whose pace and sublime running angles left him, though that was a slower process, due to injuries more than age (he was only 27 when the axe fell). Many still feel the All Blacks' ill-fated 2003 Rugby World Cup campaign might have gone better with "Cully" there.
In another example of the invisible wall that sometimes blocks the path of gun speedsters, 33-year-old Ben Smith has become largely a bench player in his final All Blacks campaign.
In his two appearances thus far, he has fallen behind Beauden Barrett as a fullback and behind Reece, Bridge and Ioane as a wing, though his start at 15 against Namibia could help find his form. His is still a significant talent to bring off the bench but that slashing, tackle-beating, sinuous running does not seem as effective as it used to be.
So it will be interesting to gauge Jordie Barrett's progress at this World Cup, particularly with his time at 10 against Namibia. He played well against Canada and, though Steve Hansen has jerked his chain a bit at this tournament to contain the youngest Barrett's impetuosity, he is obviously the successor to Smith.
Jordie has his detractors but he has speed, height, high ball expertise, long range goal-kicking and can play fullback, wing, midfield and first-five. As he hones his skills — and gets his head right — he is set to be an important part of the team from 2020 on.
As for Ioane, Howlett's long-standing record of test tries could be under threat if this strapping 22-year-old rediscovers the magic.
Savea currently holds the title of best All Blacks' test try scoring rate (85 per cent with 46 tries from 54 tests); Cullen and Howlett's rate was 79 per cent.
Ioane's is currently 88 per cent, though, as Rokocoko, Cullen and Savea all discovered, tries dry up a bit as age, injury and defences catch up.
But there's a strong sense Ioane has unfinished business, just as Rokocoko did.