And Haumono's improvement has been plain to see, says Fortune.
Parker, 24, and with confidence sky-high after his points victory over Carlos Takam in Manukau in May which earned him his mandatory title shot, will know Haumono's only chance for victory is via a stoppage, and he will be looking for a similar finish to prove he has learned the lessons of his last, tough, fight.
"We've had 60-65 rounds of high-quality sparring," Fortune said. "That's why Joseph is based in Vegas, for that quality of sparring opponent."
It is the first time Fortune has worked with Haumono, a former league player who has fought 28 times as a professional, with 24 victories.
"I wished I'd got him four years ago," Fortune said. "I didn't know what Sol was about, but he's a natural athlete who gives me 100 per cent and so I give him 100 per cent. If I had to struggle and battle to get him to work I wouldn't bother."
This, however, will easily be the biggest fight of Haumono's career, and it comes after an ordinary performance against Manuel Alberto Pucheta, 44, in Brisbane in April.
Haumono won the fight by knockout in the sixth round, but looked gun-shy at times against a rival who was cagey but clearly well past his best in terms of physical condition.
Haumono threw the occasional powerful right hand - his most potent weapon - but couldn't put together meaningful combinations and appeared overly cautious.
His best scalp is probably Brazilian Marcelo Luiz Nascimento, whom he beat in Melbourne in 2013, and who Parker has also beaten.
But questions remain about Haumono's ability to handle the enormity of the occasion at Christchurch's Horncastle Arena against an opponent who has arguably the quickest hands in the division.
But Fortune said Haumono had improved "1000 per cent" since his win over Pucheta.
"That wasn't a great fight, that's not something you should go on, that's for sure."
