"Sonny Bill ... he's another challenge," says the cousin of former Warriors stalwart Tony Tatupu and former Manu Samoa 1995 World Cup flanker and Wigan league forward Shem Tatupu. "I can't really afford to be thinking about anything other than fighting Joseph."
In fact, Tatupu is not thinking too hard about Parker either. Already friends, the pair have sparred for each other when they have had fights in the past and have great respect for each other.
"We do respect each other but I just can't afford to think of him too much as a friend. We both have a job to do."
So, while Tatupu has a million reasons, all of them Australian, to be thinking about something other than his fight against Parker, he is staying on course mentally for that clash - and credits his job at St Luke's Timber as a steadying influence.
"I love this job. It is pretty much where I get most of my fitness from and the enjoyment of working outside," he says. "Plus my boss, Brian Glamuzina, has been really good to me; he's let me have time off work to train for this fight."
Train he has - full-time for the past month with trainer Chris Martin, working out twice a day in a mixture of fitness and ring work.
"It's really different and I have learned a lot; it's God's blessing that I have a guy like Chris Martin in my corner."
Originally an Eden rugby player who went to Panmure's Shamrock Boxing to keep fit, Tatupu has fought 13 times in three and a half years; his last fight saw him avenge an earlier loss to Junior Pati and win the vacant New Zealand National Boxing Federation title in April.
Of his nine wins, seven were knockouts and manager Jim Johnstone says his four losses were the result of "sheer inexperience".
"Everyone is underestimating him," he says. "He has got a knockout punch and that always gives you a show. He is a hard worker, he is working to the nth degree right now. He wanted this fight even before the money was brought up - he just wants to measure himself against these guys and that's a powerful motivation all on its own.
"Okay, he's had a couple of losses but they were down to sheer inexperience and he is a lot better placed now. Obviously he doesn't have the same level of stardom and exposure that 'Prince Joseph' does but he really wants this fight."
His wins include a victory over Richard Tutaki - at one time proposed as an opponent for Williams - and his only loss in the past two years was to well-performed young Japanese heavyweight Kyotaro Fujimoto in Japan. Fujimoto has also fought and beaten a Williams opponent, Clarence Tillman, and US-Kiwi Chauncey Welliver..
"I can tell you, if Afa gets past Joseph - and he can do it - he doesn't need any extra motivation but that fight against Sonny Bill ... Afa will go through the roof."
For now, however, it's all about keeping feet on the floor, and Tatupu always has the timber yard to remind him about floors and roofs.
