"It's up for him and his family to decide what he wants to do with his [next] career step. I think most New Zealanders who appreciate what he's done would put his thoughts first and wish him all the best.
"He's a fairly strong family man; he sacrificed a lot last season for the Warriors and New Zealand Rugby League. He's given that club a fair bit over the last few years, he's been their leader and I think he's done that really really well."
Douglas described the mooted switch as exciting for rugby.
Tuivasa-Sheck is no stranger to New Zealand's national game, having played for Otahuhu College 1st XV as well playing for the Blues development squad as a teenager. In the New Zealand secondary schools team he played alongside All Blacks Ardie Savea and Ngani Laumape.
It has been a decade since Douglas mentored Tuivasa-Sheck on the field, but he knows how good he can be.
"He was electrifying quick over 10 metres, amazing footwork and the ability to do that at full pace was certainly something that stood out then. Defensively was very aware.
"He's obviously physically a lot more mature now; he understands his game pretty well. It'll be fitting into how the defensive patterns of rugby work these days in that back three, if that's where he plays."
What position he does play nowadays is a completely different kettle of fish. New Zealand rugby is always deep across the park, but right now outside backs is arguably the country's richest commodity, particularly considering Damian McKenzie struggles to nail a place on the All Blacks' bench.
Thus playing somewhere else in the 15 may be the way to go for Tuivasa-Sheck - a typical fullback.
"Wing could be the place to start that, and then mould him back to fullback. I could actually see him at centre long term. Defensively reads really well… his ability to straighten up on attack and put others in space could be a real asset there too," Douglas says.
"My one concern with fullback for him would be his kicking game. The way teams are playing these days… they don't want to give away a lot of penalties; they tend to want to play the game in certain parts of the field. I'm not saying Roger can't kick… but that would be my one reservation.
"You want a big voice back there so it means someone who understands the game very well. To be fair to him you want to give him time to settle in to rugby. He will, but it's not going to happen overnight."
By contrast, Douglas believes it is clear which Super Rugby club Tuivasa-Sheck will line up for.
"The Blues is obviously the logical fit for him," he says.
"He lives in Auckland, his family's all there, that's where he grew up, it's where he played his first franchise-type rugby."
Should the move be confirmed, Tuivasa-Sheck will leave behind a fruitful rugby league career. He joined the Warriors in 2016 - following four seasons with the Roosters where he won a Premiership - and took over the club's captaincy a year later from Simon Mannering. He helped guide them to a drought-breaking finals berth in 2018, a year in which he also won the Dally M medal – the first Warrior to do so in NRL history.
