Tszyu, the top-ranked contender for the WBO world title, shed 7kg to hit the scales at 69.3kg on Tuesday while Spark weighed in at 69.66kg after stepping two divisions for the biggest fight of his life.

"It doesn't matter. Just means he's got big balls," Tszyu said of the usual physical disparity between the pair.

With 11 knockouts from his 13 fights, and just one loss, Spark is a late replacement for no-show Michael Zerafa in a huge disappointment for boxing fans.

But the 24-year-old former youth world champion was again talking up his chances, as he has since receiving the call-up last week, saying he too harbours global ambitions.

"I'm feeling great. The time for talk's over and I'm coming for war. I'm coming to take Tim Tszyu out tomorrow. It's business now," Spark said after the pair exchanged words at the weigh-in face-off.

"I'm going to win at all costs. I'm winning this fight tomorrow night."

The undefeated Tszyu has heard it all before and is predicting his 15th knockout victory in his 19th professional fight.

He even whispered as much in Spark's ear.

"I'm just letting him know the dream ends tomorrow. Back to reality," he said, adding Spark's nice-guy image in front of the cameras was likely just a front.

"You don't know who he is just by doing interviews."

Despite his confidence, the 26-year-old said he'd trained just as seriously for Spark as he was preparing for Zerafa, who cited COVID-19 concerns for not leaving Victoria to fight in NSW.

"I'm always well prepared. I live by this," Tszyu said.

"I've been living by this for my whole life so I only know how to do one thing - to train hard and to fight even harder."

Asked what he thought about Spark's comparisons to the Rocky Balboa story, a no-nonsense Tszyu repeated: "Tomorrow night it ends".

"There's only one way. Everyone knows it. I know it and even he knows it."

Tszyu is biding his time for a world title shot at American champion Jermall Charlo.

In the co-main event, Queenslander Liam Wilson will fight Philippines' defending champion and world No.7 Joe Noynay for the WBA Asia Pacific super featherweight title.

Australian Associated Press