Looking at it objectively, it's probably his only chance, and it's a scenario Parker and trainer Kevin Barry will be desperately wanting to avoid.
Today, in their first press conference together since the fight was announced, Barry joked it could be a "phonebox fight", with Tupou's trainer Jeff Fenech replying: "All right, well, we hope so".
There were smiles and jokes between the two parties - Fenech and Barry's friendship goes back more than 30 years - but the intent was obvious.
Tupou, 32, a big man without the skill or fitness of the 23-year-old Parker, will want to turn on the pressure and hurt the New Zealander from the opening bell.
In sparring against Australian heavyweights Lucas Browne, Solomon Haumono, Kali Meehan and Peter Graham in Sydney, Tupou has more than held his own, Fenech said. There was a suggestion of knockdowns by Tupou in training - including kickboxer Graham - although Fenech wouldn't elaborate out of what he said was respect for the fighters.
"I believe the only way Bowie can win the fight is by knockout," Fenech said. "Obviously we've trained to knock Joseph Parker out. Bowie is a nice, modest guy but if you've seen what Bowie has been doing in the gym over the last six weeks to opponents... Bowie has caused a lot of damage in the gym."
Asked if Tongan-Australian Tupou can lure Parker into a stand-up brawl, Fenech said: "Definitely so - he's got to. For us to win we've got to make Joseph fight. Of course we're going to make him fight. When someone is six inches away you've got to punch - especially a guy who is 120-125kg and punching consistently. You've got to punch, it's no use catching punches."
Barry said it was "a very good fight plan from Jeff", adding: "We've trained very hard to prepare for 12 rounds. The fight might only be one round, but if it's 12 rounds I can promise you that Joseph will still be up on his toes and sticking that jab in your face at the end of the 12th round."
The stakes will be high for both fighters at Stadium Southland in front of a crowd of about 4000 - the biggest Parker has fought in front of. A Duco spokesman said 80 of the 81 corporate tables had sold and there were fewer than 100 general admission tickets remaining.
Parker, ranked eighth on the WBO list, will move into the top five of the organisation if he beats the Tupou, who is ranked 13th. A win for Tupou would likewise shoot him up the rankings.
In talking about the need for his man to fight intelligently, Barry was asked about Parker's fight against Afa Tatupu 18 months ago in Auckland, the last time he fought a fellow Polynesian.
It was a brutal bout which ended in success but also a nasty head cut from a head-clash for Parker, who had felt the need to prove his toughness.
"Everyone knows I wasn't very impressed with the way Joseph followed the game plan in that fight," Barry said. "That fight was a year and a half ago - this is a different guy standing beside me here today."
