Former Australia Sevens coach Michael O'Connor has been left gobsmacked by Jarryd Hayne's latest code swap, saying it is a massive ask for the former NRL star to adapt to rugby's shortened form and represent Fiji at the Rio Olympics.
The Australian sporting spectrum went into meltdown early Monday morning (AEST) as news of Hayne's shock retirement from the San Francisco 49ers and the NFL spread across the country.
The former NRL star walked out on rugby league at the end of 2014 to pursue his dream of playing American football at the highest level; but after little more than 18 months in the game, he's decided to chase another dream in participating at the Olympic Games.
O'Connor can't see it happening.
A dual international himself, O'Connor was in charge of Australia's Sevens program between 2008 and 2014. He remains a keen observer of Sevens today, and can't fathom how Hayne can transition to one of the most demanding aerobic sports on the planet in such a short space of time.
"I think if you asked the coach, Ben Ryan, I don't know what he's said about this but I'd be very, very surprised if he could get transitioned in two months," O'Connor told ESPN.
"A lot of the athletes that [Ryan] has over there, they've been in a Sevens program for three or four years and he's got a squad of 30 or 40 players who, you know, athletically are as good as Jarryd Hayne in my opinion.
"But they've been conditioned, they know Sevens, they've been playing it and they've been preparing for it and for someone to come in at this late hour with two months to go before the Olympics ... they're a successful side as it is.
"I could understand if it was Brazil or a side that was lacking talent, but they're the world champions. I just can't get my head around it."
While Hayne could conceivably recover many of the skills from his time in the NRL, rugby's shortened form is a totally different beast.
Wallabies playmaker Quade Cooper has already had his Olympic dream quashed, and Hayne will have even less time to adjust and convince Ryan he is worthy of a spot ahead of the existing Fijian players who've grown up with the game all their lives.
"[Ryan's] got 40 athletes in his program who are all similar to Jarryd Hayne and they play Sevens," O'Connor told ESPN.
"They've been brought up with the game, they understand it, they understand in certain circumstances little nuances within the game; when to kick and when not to; how to wind a game down; what stage of the game you need to slow the game or quicken it up.
"So, you know, it's that game knowledge, that's what I'm trying to say; he just wouldn't have any of that game knowledge - it would be a massive ask."
Hayne's biggest hurdle seemingly will be the complete change in fitness systems, going from the short, sharp bursts of raw power required in the NFL to the prolonged periods of running in Sevens.
And he may get the chance to sample just how tough that is this weekend, with Ryan confirming Hayne is under consideration for the final Sevens World Series leg in London.
O'Connor likened the aerobic demands of Sevens to that of an Australian Rules football player.
"And that's the other thing, the game is such an aerobic game," O'Connor said.
"Nick Poulos, the guys who does our strength and conditioning for the Australian side and formerly worked at the Adelaide Crows ... these guys are running, they're similar sorts of athletes to the AFL and possibly even better with the data that he's got around running intensity and GPS, and metres to minute, all that sort of stuff.
"You've really got to have an engine on you and you've got to go back-to-back. And you've got to have that aerobic fitness - the game doesn't stop. You can't walk anywhere. So to pick that up in two months, just that alone, would be very difficult."