Former All Blacks legend Sir John Kirwan has labelled Kalyn Ponga's potential move from the NRL to rugby union as "high risk" and warned the youngster that it will take more than one season to find his feet in rugby union.
The 21-year-old has reportedly been offered a $A4.5 million ($NZ4.7m) contract by his current side, the Newcastle Knights, to keep him at the club until 2023.
His upgraded contract offer includes a clause to jump to the XV-man code in the final year of his contract to let him chase his childhood dream of representing the All Blacks at the 2023 World Cup in France.
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However, Kirwan told the Sydney Morning Herald that Ponga will need more than one season in rugby union if he is intent on making the All Blacks' World Cup squad in three years' time.
"I don't think he could do it in one year," the 63-test ex-All Blacks star said. "It would be high risk on his part. He could take that risk if he wants, but this All Blacks team has some guys who are pretty big competitors and like to succeed. I think he needs two years. He's got nothing to lose. A two-year contract and if it doesn't work out he can go back to league.
"This has nothing to do with money. For guys at this level, what I've realised is that they want a different challenge. I believe that's what Kalyn wants, and if he wants to have a crack then it won't be about money. He's got the ability man, for sure. He's got the ability, he just has to decide which position and I think he's more a 10 or a 15."
Kirwan, who switched codes himself when he joined the Auckland Warriors in 1994 after representing the All Blacks for a decade, has experience to back up his theory.
While coaching the Blues between 2013 and 2015, Kirwan recruited NRL legend Benji Marshall from the Wests Tigers to join the Auckland franchise for the 2014 Super Rugby campaign.
The acquisition of the one-time NRL champion and 28-test Kiwis star proved to be a failure, though, as Marshall only made six appearances before switching back to rugby league to link up with the St George-Illawarra Dragons.
Kirwan suggested there were lessons to be learned from Marshall's failed code switch for both himself, Ponga and any other potential code-hoppers.
"Benji just needed more time in the game and, sadly, I didn't have that time in the game," Kirwan told the SMH.
"He would have been fine had he come over earlier and I was able to give him more time in the saddle. But we started losing and then all of a sudden you find yourself under pressure and I had no time to give him the attention and time he needed.
"In the end it was a mutual decision that 'This is not working out'. I was really down about it to be honest, because I felt the situation let him down."
Given his age and background, though, Kirwan said he believed that Ponga has two key factors working in his favour which Marshall didn't have.
"It's better to do it when you're younger, and you've got a background in the sport, which Kalyn ticks both boxes. Guys who have played rugby at school, guys like Solomone Kata, who is now on the wing for the Brumbies … it's going to be a lot easier.
"I'm pretty sure if Roger [Tuivasa-Sheck] wanted to come over it would only take him a couple of games and he'd be all good."