But to get into Fiji's team with less than three months until the Rio Games appears to be the most daunting sporting challenge he's ever faced.
"He's been in the gym getting ready for the Dodgem Car-like collisions that is NFL, getting belted, where as in Sevens it's about running. He's ready for the wrong sport," former Wallaby Greg Martin told Triple M Brisbane's Marto & Ed Kavalee for Breakfast.
"He doesn't understand the laws of the game. I keep saying the difference between rugby league and rugby union ... what happens after you get hit is where the game begins to differentiate. When you get hit in rugby league everyone has to leave each other alone and go backwards and get ready for the next hit.
"In rugby union that's when the game begins, and he was making tackles and running away. That's instinct. You don't change instinct in one day and you won't change it in six weeks. He's got no chance."
Hayne conceded he had a lot of work to do. "At the moment, I'm behind the eight ball and I've got no problem with that. It's about working hard and getting there," Hayne said.
"They're the world champs. Sometimes in life, it's not about success, but it's about the experience and just being part of that team.
"(It's the) first Fijian team to win back-to-back titles and they've got a bunch of superstars who are going to be a joy to train with and a joy to play with.
"It's not about coming over and making the team, it's about giving me an opportunity to make a team."
Hayne now faces six weeks of intense training in Fiji to prove to coach Ben Ryan that he's not only fit enough for Rio, but good enough to displace one of the team's established stars.
"Our cupboard is not just deep, it's absolutely littered with fantastic talent," Ryan said.
"We had a very light week this week ... when we're running up 100-metre sand dunes, when these guys are the fittest rugby players Fiji has ever had and they're still throwing up after sessions, his lactate's going to be going into overdrive.
"Whether he'll be able to tolerate that in a short time frame is a serious question."
Hayne had a huge amount to do to compete, Ryan said.
"This isn't just a random side, this is the best side in the world in the last two years.
"A Fijian side that plays a very high-tempo, high-risk game that requires enormous amounts of skill and he has that, and enormous amounts of fitness, and he hasn't got that at the moment."
Fiji finished clear of South Africa to win the Sevens World Series for a second year running, having made the semi-finals in all but one tournament this season.
Ryan's team finished fourth at Twickenham, losing 26-19 in the third-place playoff against USA.
