It’s the most important fight of his life, and Tim Tszyu has promised to deliver an upset win for the ages for Australia.

A defeat against one of this generation’s greats in Errol Spence could spell the end of his world champion career, but Tszyu is adamant he will celebrate a momentous victory with the Aussie flag draped over his shoulders.

Tszyu is the underdog but neither he, his father Kostya, nor brother Nikita have ever lost a professional bout in Australia.

He doesn’t plan on breaking that streak, and says he’ll lean on the local support to cause the boilover.

“I’m doing this for a bigger purpose than just myself – it’s to represent Australia on the world stage,” Tszyu told Code Sports. “We need people banging on the door of his hotel room at night time like at the World Cup.

“The enemy is on our territory, and it’s gonna be hostile.

“It’s us versus America, and us versus the world.”

Tszyu tipped the scales at 159.95 pounds, with Spence weighing in at 158.95 for the 160-pound fight that has kicked into overdrive with Tszyu’s partnership with Australian boxing legend Jeff Fenech.

“It’s really a throwback to so many other generations,” Tszyu said. “People from Jeff’s generation, to my dad’s and to now.

“Everyone can relate to it. Everyone can have their story and follow ours.

“It’s about what Jeff did, and now with our collaboration, it’s about what we’re doing together.

“But I feel like there is a lot of love and support.

“I feel it on the street. Going out, people are really backing me and getting behind me – the real Aussie way.”

The build-up has been respectful but tense, with snubbed handshakes, questions of respect, and threats of retirement thrown back and forth.

There were dramatic scenes when cocky co-main event fighter, Stephen Fulton missed weight on Saturday morning by a whopping nine pounds.

The American had already brushed Thursday’s mandatory open workouts, and requested a weight change because he was struggling.

His fight with Aussie hero Liam Wilson is now off the card completely, and behind closed doors, all the Aussie fighters on the card feel it’s a huge sign of disrespect.

For Fenech it continues a long history of American boxers showing contempt for Australians.

“There was Jerome Coffee, Steve McCrory, Greg Richardson who all came down here from America thinking that we’re all nobodies,” Fenech told Code Sports. “They all fought me, and I don’t think any of them even won a round against me.

“I’d like to think Tim can duplicate that.”

Two years ago, Tszyu was close to relocating to America, but now says that would have been a huge mistake.

“This is the first fight camp that I really realised that I’m Aussie and I’m better at home,” he said. “The other day I was looking out at the Opera House and Harbour Bridge and was just thinking how blessed I am.

“Why would I want to go to America?

“We have the best people on Earth, and the best country on the planet.

“I’m not moving for anyone.”

Tszyu & Spence Jr. go face-to-face

Sitting on the edge of the stage after weighing in at Darling Harbour on Saturday, Tszyu revealed his plan to inflict pain on Spence from early on.

“I want to shock him and want him to have flashbacks of his last fight,” he said, referencing Spence’s one-sided defeat to Terence Crawford – who was in the building for the weigh-ins and will be ringside on Sunday afternoon.

“I’ve got a legend in front of me, and I know what it takes. I understand that this is a crazy task in front of me.

“I’m ready to prove a lot of people wrong.”

Spence has been incredibly laid back all week, and gave a simple last comment before escaping back to the hotel with his massive entourage.

“Thanks everybody for coming out,” he said. “There’s nothing else to say. It’s fight time and I’m ready to go.”

After Wilson’s fight was cancelled, the all-Sydney showdown between rising star Ahmad Reda and veteran Paul Fleming is the new co-main event.

A five round heavyweight bout between Brandon Grach – who scored the knockout of the year in 2023 over Liam Talivaa – and Ike “Ike From Pluto” Enyi has been added to the card.