"It's going to be more physically demanding than mental, with the amount of running we're going to be doing. It's a challenge in itself and I'll just have to wait and see whether I can make it."
Hayne was confident in his capability of adapting to sevens, having proven himself a quick learner when with the San Francisco 49ers last year.
But after opting to chase another challenge following a year in billion-dollar industry that is the NFL, the 28-year-old said his new career move required a different kind of adjustment.
"That was part of the reason I came back - humbling myself and, being around the guys, being humbled. You go from facilities where you have everything at your beck and call to facilities like this. That's obviously very humbling but the hard work is all that matter."
Hayne has already endured a humbling introduction to the sport, playing limited minutes at his first event in the London Sevens.
And with Fiji having claimed the world series title, competition for places was certainly fierce.
"Not being there for the majority of the tournaments was obviously tough and I have to learn pretty quick," Hayne said.
"But, as you saw last year, I was able to learn very quick and was able to make the team. This is another challenge."
Hayne faced a different type of challenge altogether when attempting to lure his former 49ers teammates down to the Pacific Islands, with Fiji Airways tonight beginning a direct route from Nadi to San Francisco.
While many were interested in what Hayne's homeland was like, getting Americans out of America was easier said than done.
"Americans don't really travel that much but it's good for them to come and explore different cultures, and I've got no doubt that they'd enjoy it."