Ustinov's camp is waiting to learn the results of Tua's MRI scan following the Kiwi heavyweight suffering a grade one tear to his calf during training.
"Any delay would not be good, but it would depend on how long the fight was put back," said Ustinov.
"If it's only a week there is no point in going home. It's a 30-hour flight so as soon as I got there I would have to turn around and come back.
"But if it's a month we might think about what our actions are. If it's a serious injury I don't think a month would be enough, but of course, it all depends on Tua."
Ustinov said Tua's name still rings out throughout the heavyweight division, meaning the winner of this fight will put themselves in the frame for a potential world title shot.
"He still has a good name and is well known for his strength and his famous left hook, but I think he will have to work really hard to stay in that position.
"I think Tua and I have the same opportunity to get closer to the top."