Wallabies great George Gregan welcomes Jarryd Hayne's switch to Sevens rugby, but doubts he'll crack into Fiji's Olympic squad in such a short time.
Hayne became arguably the sport's highest profile recruit a week ago when he unexpectedly walked out of the San Francisco 49ers to link up with the Fijian sevens team in London, with his motivation being to play at the Rio Games.
Gregan says his desire is admirable, but thinks earning a spot in Fiji's Olympic team may prove a bridge too far for Hayne.
"He could prove me wrong. He's played eight games of NFL in under a year," Gregan said in London while attending the final round of World Rugby Sevens.
"Sevens is a challenge. It's not that easy.
"Ask Sonny Bill Williams, ask Liam Messam, ask the Honey Badger (Nick Cummins), ask Quade Cooper.
"It's not that easy just to think you flick a switch and can play Sevens. It doesn't work that way."
Gregan, capped a record 139 times for Australia, is a huge fan of the abbreviated version of the sport and is an HSBC ambassador for the World Rugby Sevens series.
He expects the Rio Games will catapult the sport into the international mainstream.
Two-time Dally M medal winner Hayne is not the only NFL man keen to explore the avenue of sevens rugby.
New England Patriot and Super Bowl winner Nate Ebner is also eyeing a trip to Rio with the American Sevens team.
Ebner boasts a rugby background and has returned to his roots.
"I think rugby sevens has that appeal," Gregan said.
"It's attracting people like Jarryd Hayne, like Ebner, who's still playing for the Patriots and wants to play in the Olympics and wants to win a gold medal for his country.
"That's a big carrot to put in front of any athlete."