Last night's award is even more remarkable given Tuivasa-Sheck carried the burden of being a young captain all through 2018, and was still learning his trade as skipper.
He was also the face of a franchise that had copped so much criticism last year, and was written off heading into this season.
And while he had a number of good lieutenants beside him – with Tohu Harris, Adam Blair, Blake Green and Simon Mannering et al – he was captain of a group of men that often needed a lot of leadership.
But that didn't faze Tuivasa-Sheck.
His answer was to work even harder, narrow his focus and constantly look to improve his preparation.
The results have been spectacular, as the 25-year-old had an extraordinary season.
In many of the Warriors' 15 victories he was a good portion of the cake, as well as the icing; the grit and the glitz.
He was also remarkably consistent; even when many of his teammates had an off day, Tuivasa-Sheck was invariably on.
Remember the fateful 27-26 loss to the Bulldogs in Sydney?
Most of the team were strangely flat, but the fullback ran for more than 250 metres, scored a try, made a line break and did everything he could.
Much of the focus has been on Tuivasa-Sheck's attacking deeds this year, with his slashing breaks, bundle of try assists and relentless capacity for work.
He averaged 178 running metres a game - only two players in the NRL managed more – and was second in the competition with kick returns, while also contributing 112 tackle breaks.
But his defensive qualities were also telling.
He led the NRL for try saving tackles (six), with last ditch stops that inspired his team and turned momentum. It all started in the 5th minute of the first game of year, against the Rabbitohs in Perth.
His South's counterpart Alex Johnston had looked certain to score after being put into space, but Tuivasa-Sheck stopped him in his tracks a metre from the line, then drove Johnston over the sideline with perfect technique, brutal strength and sheer will.
There were similar efforts against the Titans (round two) and the Raiders in Canberra (round three) which set a 'follow me' standard that never really abated.
Tuivasa wasn't renowned as a defender when he arrived at Mt Smart three years ago, but has worked tirelessly on that side of his game.
"I don't think I've seen too many with his drive to want to be the best," reflected Warriors assistant coach Andrew McFadden earlier this year. "He is constantly working on his game and that is probably his defining quality. Some talk about wanting to be the best, but he lives it."
That work ethic isn't new – it's been evident since he was 10 or 11, and doing extra sessions before training with his father in Otara.
"A lot has come from my old man," Tuivasa-Sheck told the Herald earlier this month.
"He's a tough crowd to please. All he cares about is am I improving, am I getting better. That's the sort of person he is and I think I have picked that up from him."
