Tupou has been a bench forward in four of Australia's six Tests in 2021, playing just 52 minutes in the two Rugby Championship defeats to New Zealand.

While it's obvious Rennie is attempting to use the Tongan Thor's running power to expose tiring defences, Tuqiri thinks it's a flawed strategy if Tupou's introduction comes at a time when a game is already too far gone for him to change the result.

He says Tupou is obviously a first-choice front-rower, particularly after the Springboks named a monster pack and the 25-year-old brings 132kg of grunt to the Wallabies pack.

"Maybe I'm old school, but I'd play my best XV. I'd start with my best XV and then let everything else get dealt with after that," Tuqiri told AAP at a promotional event for Australia's 2027 Rugby World Cup bid on the Gold Coast.

"I know you probably want to bring him on when things have cooled down and people are tired and he can use his destructive running a little bit more.

"You'd tell him that but I think for Taniela, he probably wants to start as well.

"So you've got to wonder what that's doing for his confidence from a mental point of view.

"For me, I want my best XV starting - I'm starting Taniela Tupou."

Tuqiri is however a fan of Rennie's decision to add 38-year-old Greg Holmes to his squad before the clash with the Springboks at CBUS Super Stadium.

An injury to Pone Fa'amausili opened the door for Holmes, who last played for the Wallabies in 2016.

Tuqiri says whether Holmes plays or not, the decision will benefit Australia ahead of some vital scrum battles against the Springboks and Argentina.

"Whether he plays or not, I don't know, but I think he's great to have in the squad as a bit of a mentor to the younger blokes," he said.

"Everything like that helps when you're facing the All Blacks in a Test or you're facing the Springboks. That's where their games are won and lost."

The Wallabies are also under pressure to temper down an expansive, ball-running style of football with the All Blacks ruthlessly punishing skill errors throughout this year's Bledisloe Cup campaign.

Tuqiri, though, believes there's nothing wrong with the Wallabies attempting to build their own playing style and is urging them to persist with it.

"When you've seen Wallaby teams of the past, successful Wallaby teams of the past, they have their own style," said the dual international.

"You watch New Zealand, they have their own style. South Africa has been lambasted for the style that they play but it's a winning style.

"We're slowly getting there. We like playing with the ball in hand ... we've got the players to make that work. We just have to believe in it.

"Those sort of things are hard to believe in at times or you lose a bit of confidence when you aren't winning. So they've just got to believe in the persistence of what they're doing."

Australian Associated Press