Junior dos Santos is angry - which doesn't happen very often.

Known as one of the nicest guys in the UFC, it's rare to hear JDS get worked up.

For years he's avoided the kind of trash talk that fighters like Conor McGregor revel in, but with his headline fight opposite Tai Tuivasa now five weeks away, he's dropped the good-guy routine.

The source of his rage is his 25-year-old up-and-coming opponent.

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More specifically, it's Tuivasa's claims to be a "street-fighter."

"In his last fight, with Arlovski, when Bruce Buffer was introducing him, he said he represents street fighting," dos Santos told Sporting News from his training base at American Top Team in Florida.

"I was watching the fight last night, and saw that and was like 'what?! That's not even a martial art.'

"I thought I was fighting against a martial artist, but that's not the case. I want to know more about this, and one day I'll ask him.

"To represent street fighting...that's just stupid. Who fights in the streets? It's not even fair. That's a coward.

"Street fighting is not a martial art - it doesn't exist. How can someone represent street fighting - that's bullshit."

Tuivasa, who proudly represents Western Sydney, is ranked 11th in the heavyweight division after just under a year in the UFC.

He makes no excuses for, and doesn't hide from, his sometimes rough upbringing, and has earned a legion of fans for his exciting fighting style, funny post-fight comments and, of course, the Shoey.

Dos Santos wasn't interested in any of that.

According to the Brazilian veteran, Tuivasa is disrespecting the sport by bringing up street fighting.

"Everyone, all the gyms around the world, are fighting against that - against this kind of stupid thing, this coward thing," dos Santos said.

"It doesn't exist. You're not a street fighter, you're a coward. These people who fight in the streets don't really know how to fight.

"Come to a real gym, face a real fighter and you'll get your ass kicked. And if this guy, Tai Tuivasa, is really a street fighter, that's what he's going to have - he's going to have his ass kicked by me on December 2nd in Adelaide."

After two first round stoppage wins in his first two UFC outings, Tuivasa is coming off an impressive three-round decision win over Arlovski. It's the bout that has dos Santos so fired up.

All three of 'Bam Bam's' have featured impressive stand-up, but dos Santos says that won't work come fight night.

"He put in a good performance against Arlovski, but that doesn't matter - I'm gonna go in there and knock him out," Cigano said.

"This is my first strategy. Whenever I fight, I'm going for a knockout. And I'm gonna knock this guy out.

"I know he likes to stand up and bang, so it makes it more special."

Dos Santos, who bounced back from a first-round TKO loss to then-champion Stipe Miocic with a hard-earned five-round win over Blagoy Ivanov in July, knows the crowd will be against him, but had a message for the Aussie fans.

"They'll be going for their guy, and I like the Aussie fans and their energy for the sport," he said.

"I appreciate that, but I'll have to give them some hard tips. Their guy will get his ass kicked on December 2nd.

"Either way, I'll be there to celebrate. I'll be celebrating my win, but if they want, they can join in."

When contacted for a reply, Tuivasa - who is midway through training camp at Tiger Muay Thai in Thailand - had a blunt response: "Tell him to go f**k himself."

Bring on December 2.