The 29-year-old, who weighed 81kgs for his maiden fight, has packed on considerable size from his days as an outside back on the league field and he tipped the scales at 108kgs when he beat David Levi via unanimous decision to claim the vacant Australian heavyweight title in Sydney in December.
Six months ago, Sam (10-2-2) left the army and now works as a personal trainer and a bouncer to supplement his income from boxing but his need for money may change in a few days.
The Queenslander has been given a wildcard spot in Wednesday's Super 8 tournament in Auckland, which has a $500,000 purse, where eight fighters have been matched and the pairs will meet over three three-minute rounds until an overall winner emerges to claim the $200,000 first prize.
In the first round, Sam has drawn Kiwi-born veteran Kali Meehan who hasn't fought in more than two years.
At 44, Meehan is in the twilight of his career but sparred with Australian Alex Leapai before he unsuccessfully challenged world heavyweight champion Wladimir Klitschko in Germany in late April.
Meehan has also built up for the Super 8 by working with Australian-based Tongan Bowie Tupou and his teenage-son Willis who is a top amateur boxer and rugby league player, while Meehan's monster 1.96m frame is a challenge for anyone.
During a lengthy professional career, Meehan has built up a 38-5 record and nearly claimed a piece of the world heavyweight title when he was edged by American Lamon Brewster in a split-decision loss with the WBO crown on the line in 2004.
Wednesday could be a life-changing day for the 1.85m Sam but he will enter as an underdog against Meehan.
"I've won three titles in the last 12 months and each time I've been the dark horse and I like to be that. Just a real no-name and just go with the flow," Sam said.
"Hard work does pay off if you want to make the sacrifice."