Former Australia captain George Gregan says he cannot fault Jarryd Hayne for "chasing his dream" of representing Fiji at the upcoming Olympic Games. 

Hayne, who left NRL outfit Parramatta Eels in 2014 to pursue a career in the NFL with San Francisco 49ers, announced earlier this month he would be retiring from American football, confirming his intention to play sevens at the Rio Olympics.

The 28-year-old was one of 12 men selected in Fiji's squad for the last round of World Sevens Series in London.

While Gregan, who won the 1999 Rugby World Cup with Australia, admitted he was disappointed to see Hayne leave the NFL, he insists there is nothing wrong with his decision.

Ex scrum-half Gregan told Omnisport: "It’s a hard one. The decision has been made by Jarryd, if he plays at this tournament in London then he'll be eligible for Fiji.

"But isn't it cool how he's an NRL star, who has played for his country, played for NSW - which might not mean much outside [of Australia] - but he's a household name.

"He chose to leave that and go chase his dream of being an NFL player with the 49ers. He did some great things there. I think he started eight games and then had a limited role but made that transition in 12 months.

"Unfortunately from a 49ers perspective of someone who wanted to see him succeed there, he's said, 'hang on, I've got a chance to play with one of the great sevens teams' which is Fiji. Fiji is always one of the strong ones.

"And I think the one thing that surpasses all those other sports is an Olympic gold medal. Everyone dreams of being an Olympian and having the chance to play for a gold medal and become a gold-medal athlete.

"He's chasing his dream and good luck to him."

Gregan was full of praise for the "fast and exciting" rugby sevens adaption, which will make its Olympics debut in Brazil later this year. 

"Rugby sevens is on the rise," he added. "Some of the most athletic players, both men and women, showcase their skills over a game where it's seven minutes a half, a minute break, and go at it again.

"It exhibits everything about rugby on a full pitch with half the players, so there's a lot of running, moving and players blowing really, really hard because they're tired."