South Sydney Rabbitohs players and coaching staff were stunned by the size of Jordan Mailata when the 168kg and 205cm tall prop turned up for his first training session with the club's under 20s team last season.

Now Mailata is getting the same reaction from NFL scouts in Florida, where he has been training at the renowned IMG Academy in the hope of being chosen in the April 24 draft at AT&T Stadium in Arlington, Texas.

After performing the 40-yard dash in 5.0 seconds during recent testing, Mailata has attracted interest from a number of franchises who will attend a pro-day in Tampa on Saturday to assess the 20-year-old whose former team-mates described him as "unstoppable" last season.

"Playing with him in the under 20s, you just had to give him the ball 10 metres out and no one could stop him from that close to the line," Rabbitohs halfback Adam Doueihi told NRL.com. "Last year he was unstoppable, and he actually hurt a few kids because he was such a big kid."

Under the guidance of then Rabbitohs head coach Michael Maguire, Mailata managed to get his weight down to 145kg after arriving at the club during the 2017 pre-season at 168kg.

"I remember seeing him the first day he walked into the club and even Madge and the coaching staff were just freaking out about how big he was," Doueihi said.

Rabbitohs halfback Adam Doueihi. ©Robb Cox/NRL Photos

"I think he came in at 160kg or something crazy like that and he is about 6-foot-8 tall. Apparently, he is going good over in the States, they reckon the tests he has done are through the roof and they have never seen someone like that so I am really happy for him."

In 12 appearances from the interchange bench for the Rabbitohs, Mailata scored eight tries but he was only able to manage an average of 21 minutes per game.

However, an example of his impact was the 165 metres he carried the ball in just nine runs during a 22-minute stint against Melbourne Storm and the 192 metres he made from 14 carries against New Zealand Warriors.

"I would sit in the stands watching him before my game and I was always surprised at how freakishly big he was," Rabbitohs lock Cameron Murray said. "He is huge, the first time I met him we were doing weights and he had to duck down to get through the door."

It was a highlights video of Mailata's performances for the Rabbitohs, which now features on the NFL website, that earned him an invite to trial at a combine for international athletes in Los Angeles last December.

Former Rabbitohs giant Jordan Mailata. ©rabbitohs.com.au

Mailata was selected to train and live at the IMG Academy in Bradenton, Florida, which has been described as "Disneyland for athletes", and since January he has been working with a team of specialist coaches, including 2004 Olympic gold medallist Dwight Phillips.

"He has gone over there to pursue his dream so good luck to him," Murray said. "It would be good to see a Souths boy make his stamp on the NFL and do well for himself, his family and all of us here so I am pretty excited to see his journey."

In an interview with NFL.com, Mailata said he was confident of making the transition to become an offensive lineman but had a lot to learn.

"I went there not really understanding the level of athleticism and skill the guys up front at the line of scrimmage had," Mailata said. "But now having been put through the many drills and testing, it certainly opened my eyes to how good the NFL athlete is.

"I am looking forward to the challenge and feel confident I can succeed, but I now have a lot of hard work in front of me before I can start thinking of wearing an NFL jersey. This is just the start of my NFL journey."