He is giving up guaranteed riches and established fame in Australia to go after the unprecedented.

Jarryd Hayne announced last year he is leaving the Australian Rugby League as one of the sport’s biggest stars to try to make it in the National Football League. There have been others who have made this move, but most have either returned to rugby or remained in the NFL as a kicker or punter.

Hayne wants to do something different. He wants to be a position player, probably a running back.

“It’s going to be really hard for him,” said Carlin Isles, a rugby sevens player for the United States who briefly joined the Detroit Lions' practice squad in 2013. “It depends on his dedication. I think if he’s dedicated, he could speed up the process. But for him, who never played football and to understand the defensive schemes, to understand the holes, the footwork, things like that, it’s going to take some time.

“Especially if you haven’t grown up playing American football, it’s going to take a lot because it is not easy. It’s difficult to understand.”

Hayne has trained in the United States at times since the announcement and has been on the precipice of signing with an NFL franchise for months. Multiple NFL teams reportedly expressed interest, including the Lions and Seattle Seahawks, before he picked the San Francisco 49ers on Monday night.

What could intrigue them is what makes him a more attractive candidate to stick on an NFL roster than some of those before him. He is 6-foot-2, 220 pounds and according to the National Football Post, ran a 4.5-second 40-yard dash time, which would place him between fourth and 12th among running backs at the 2015 NFL combine.

“You watch a lot of his highlights and he’s got good change of motion, good direction, seems to know how to get away from people,” said Tim Dwight, a former NFL receiver who worked with Hayne in December. “He seems like he has a lot of mileage still left on him and he has a good attitude.

“He’s going to get knocked down quite a bit, not just obviously physically but mentally wise, learning all the play sets, learning his job, learning his role. You have to get him started early.”

Early is relative for Hayne, who has never played American football in a game and is entering the prime of his career at age 27. Having to learn everything and understanding how to follow blockers are two of the things Isles pointed out as potentially difficult obstacles.

There’s also a difference between looking sharp in workouts and doing it when a 6-2, 235-pound linebacker who runs a 4.4 is sprinting toward you with the aim to dislodge and annihilate. Rugby hits can be rough, but typically they are better wrapped and not coming with the same force or velocity.

Those were some of Dwight’s concerns watching Hayne. He likes Hayne's size. His speed would be adequate, Dwight said, but not game-breaking. But Hayne can catch, and if he were to end up as a kick returner and punt returner, that might be more important than anything.

If Hayne is going to make it -- either on a practice squad or to a 53-man roster -- it’ll likely be based on his ability to play special teams, a unit that is most similar to rugby.

“Special teams is probably where he needs to focus,” Dwight said. “Covering kicks. Returning kicks and, if he’s not a returner, being a guy up front. A lot of those guys are linebackers. Some are fullbacks and some are tight ends, too.

“He’s going to have to learn another trait in there to keep himself on a team because bubble players don’t last very long, maybe a year or two and then they have to move to another team.”

Even with special teams, there are things he would have to learn -- like rushing a punt and then sprinting backward -- that could come in time but would not be instinctual at first. Offensively, after watching him and briefly working with him, Dwight said he felt Hayne could project better as an H-back than a true featured running back.

Dwight’s biggest concern with Hayne is how he adjusts to taking a hit, because running backs and receivers have spent years understanding the nuance of when to fall down and how to absorb vicious contact. Isles said there shouldn’t be as much concern there because of how players hit -- minus pads -- in rugby. Isles believes the lack of experience and understanding of football concepts will hinder Hayne the most.

To deal with this, Dwight actually suggested Hayne go through mock practices and games to gain some sort of feel for what he might encounter. These are questions for teams, too, because it's going to be difficult for an organization to evaluate him. And how long would both a franchise and Hayne be willing to invest to see whether this experiment turns into more than a novelty?

Despite Hayne’s desire and physical tools, he still has a lot of learning to do.

“That’s my main thing,” Isles said. “You have to be patient. He’s going to have to dedicate and work hard, but man, if he understands the NFL, the people in that league, it’s a lot different, explosive and fast and they understand the game so much better.

“It’s going to be tough at first, but he’ll have to work really hard, I’m talking day in and day out, to understand and get the footwork and things like that. He can’t just walk in there and think he’s going to be the man, you know what I mean? Is he dedicated and willing? He’s just going to have to grind ... it’s going to be tough.”