It's unfair to say that this is Tua's last chance, given how many opportunities a boxer will be afforded in his career - but there can't be many kilometres left to run on his odometer.
Victory over the 2.02m Ustinov, who is 28-1 and has 64 kickboxing fights to his credit, would put Tua back on the map in a heavyweight division that is dominated by the Klitschko brothers, Wladimir and Vitali.
He would probably be at least one more impressive performance away from a world title shot but Tua and his knockout power is a huge drawcard.
Tua and his trainer, Lee Parore, along with David Higgins from Duco Events, fronted a press conference in Auckland yesterday to talk about the August 31 bout, which has been dubbed "David vs Goliath".
Two big questions remain about the 52-4-2 Tua.
First, what is his motivation like to train and second, does he still possess the same punching power that has seen him win 43 of his career bouts by knockout.
Parore moved to alleviate concerns about Tua's work ethic and said the 1.78m fighter was moving towards where he needed to be.
"He's on track, David is on track," Parore said. "We've done about 17 weeks of training over about the last 20 weeks. Obviously, first of all, it's just about establishing a good health basis so we can actually do the work that David needs to do. We've done some good rounds on the bag over the past six weeks. His fitness is coming up really well and we are on track."
As for the motivation side of things, Tua fielded that.
"I'm not just doing this for a 'payday' as they say. I believe it's a fire from within and I know I could sit here all day and try and explain it but I'm living it and I think it's the best thing I can do."
Parore said he was confident Tua still had the ability to deliver a big punch. "We are going to be doing our best to make sure that David turns up on the night with the goods."
A fit and motivated Tua showed what he could produce when he floored Shane Cameron in the second round of their 2009 encounter but since then he has lumbered through wins over Friday Ahunanya and Demetrice King, while he also had a draw and a loss against Monte Barrett.
The loss to Barrett in August, 2011 was the last time Tua stepped in the ring.
Tua is certainly in the twilight stage of his career but few can dispute his appeal with the New Zealand public, and they may be about to witness one more run towards the top if he turns up ready to perform in nine weeks' time against his Goliath.
