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It is understood that Duco Events, Tua's promoters, are keen to get their man into action as soon as possible should he win in order to capitalise on his excellent fitness in preparing for Ustinov, who he will fight in Hamilton on August 31.
That means all going well at Claudelands Arena - and if Tua agrees - his next opponent could be 42-year-old Serbian Jovo Pudar, a fight which could happen in New Zealand before Christmas.
An interested spectator at the Tua-Ustinov bout will be K2 general manager Alexander Krasyuk. K2 is owned and managed by the Klistchko brothers and an impressive victory for the Kiwi-Samoan will quickly get the brothers' attention.
Ustinov is ranked the WBA's 10th-best heavyweight and the organisation has agreed to put up the vacant Pan African belt for his fight against Tua. Ustinov is also ranked 7th by the IBF.
If Tua were to win the Pan African belt and beat Pudar, the PABA champion, he would be among the WBA's top five-ranked heavyweights and as such would be on a collision course with the big time once again.
The Klitschkos hold all the major belts - Wladimir is the WBO/WBA/IBF/IBO champion and Vitali the WBC champion.
Tua's title fight against Lennox Lewis in Las Vegas in 2000 ended in a disappointing points defeat, but the 40-year-old has never been knocked out and, while he hasn't fought for two years, his punching power hasn't diminished if the stories about the damage inflicted on his recent sparring partners are to be believed.
"It's completely in David's hands," Duco's David Higgins said. "From his perspective there's only one fight that he is concentrating on and that is against Ustinov ... but if he wins and keeps training well, he could go to the front of the queue [of contenders]."
Tua, who met Ustinov for the first time yesterday at a media conference, shaking his hand and greeting him in Russian, gave an insight into his training regime with Lee Parore, the man who prepared him for his stunning knockout of Shane Cameron in 2009.
"There's darkness and emptiness that I've never experienced in my whole career and I'm quite humbled that I've experienced it this time," Tua, 40, said.
His conditioning dropped away once he parted ways with Parore - his wins over Friday Ahunanya and Demetrice King counterbalanced by a draw and a loss to Monte Barrett - but now the link has been renewed Tua said he was in better shape than before the Cameron fight. Tua's last fight was the loss to American Barrett in August 2011.
"This is probably the hardest I've ever trained in my whole career. It's been a very tough road back. I've never experienced any pain like I've experienced on this camp."
Watching yesterday was Tua's giant sparring partner Julius Long, the American brought over to get the 1.78m Tua used to Ustinov's 2.02m frame.
Ustinov will be a big test for Tua and not only because of his size. At 36, the former soldier is younger and has a very good record - 28 wins and only one loss.
While Tua's record is also very good - 52-4-2 - he has had to work much harder to get into shape. Ustinov also has the advantage of fighting as recently as April - an unanimous points decision over Croatian journeyman Ivica Perkovic.