In his first sparring session in July, the Canadian-Nigerian, nicknamed Mt Kilimanjaro, was flattened by Tua. This week he was forced to stop briefly in a sparring session open to the media after a "cunning" Tua repeatedly hit him on his left thigh. His leg gave out despite the punches being too quick and discreet for most casual observers to notice.
Both that power and intelligence, honed by almost 60 professional fights and countless amateur ones, will be required by Tua against Ustinov at Hamilton's Claudelands Arena on November 16.
Belarusian Ustinov, a former soldier, is big - he is 2.02m - and has a good record. But, according to Olubowele, who is a similar size, Ustinov will offer Tua opportunities with his robotic and predictable style.
Olubowele, who has a modest professional record, did some research into Ustinov as he was considering fighting him at one stage and was relatively reassured by the results.
"He fights in a European style, very light on his feet, even though he's a mountain of a man," he said. "But he's very robotic, very predictable - the same thing over and over again. It just takes time to time it and catch him.
"I think most importantly as you saw there, David is very cunning, he's adaptable, and I think that will be one of the key components to his success because Ustinov is going to be the exact same Ustinov as he was yesterday and he will be tomorrow."
In what was a rare move so close to a fight, Tua's camp opened up the sparring session to the media at their fighter's Onehunga, Auckland, gym during the week.
Scheduled to spar four three-minute rounds with both Olubowele, with more of the same against the bigger Julius Long straight afterwards, Tua's new trainer Henry Schuster called it quits after the first bout, citing the need to keep some secrets.
Olubowele, who moved to Canada from Nigeria aged four, studied kinesiology - the science of human movement - at university and comfortably landed some good left jabs on Tua early in the session before the 40-year-old Samoan Kiwi upped his game and went on the attack.
A practising holistic nutritionist as well as an occasional actor, Olubowele said he had been impressed by Tua's movement.
"He's agile, even though he's 110kg, he's really agile and that's what helps with his explosiveness. That's what you're going to see a lot on the night. It's going to be the key to his success."
Olubowele said finding himself on the canvas in his first sparring session was partly down to fatigue - he had only recently arrived the country, but added of Tua: "He's still a powerful man. I'm 120kg and I'm not accustomed to being thrown around the ring. David hit me once and I blocked it completely, and it still threw me."
Tua's fitness coach Lee Parore admitted his man's calf injury which forced the postponement of the fight from late August, had worked in his favour.
"There's no question that it's been beneficial from David's point of view," he said. "It's given him time to put a few things into perspective and it's given him time to take a few things to the next level which is where he has to be."
