LAS VEGAS – Oscar Duarte switched back and forth between his native Spanish tongue and still-developing English, but when he heard IBF 140lbs champion Richardson Hitchins press him to bet on the outcome, Duarte went straight to crass, blunt English.

“Shut the [expletive] up, [expletive],” Duarte said.

The champion, 28, seemed astonished by the response, answering: “That [stuff] is not funny. I promise I’m going to beat the shit out of you.”

The exchange between Brooklyn’s Hitchins, 20-0 (8KOs), and Duarte raised the stakes in the title bout on Saturday night at T-Mobile Arena – the intensity of the fight spiking from somewhere around a solid seven to 10.

“I’m ready for you,” Mexico’s Duarte, 30-2-1 (23KOs), said.

Answered a bewildered Hitchins: “I’m ready for you, too. What the [expletive]? What you think? I’m going to knock you the [expletive] out.”

Hitchins is a comfortable -450 betting favorite over Duarte, who has won two consecutive Golden Boy Promotions main events and has risen to third in the IBF ratings.

“I’ve grown significantly over every fight and every punch will reveal that,” Duarte, 30, said. “I definitely think they are underestimating me, but that’s on them. I know what I’m bringing to the ring. I’m extremely happy to be here. I’m hungry and want that world title.”

Hitchins is anticipating bigger fights beyond this co-main event, with his manager mentioning a possible unification with WBC champion Dalton Smith and a later move up to welterweight to fight Devin Haney.

“The kid’s talent is endless – there’s no ceiling on him and he could go down as one of the all-time greats by the time his career’s over,” Hitchins’ manager, Keith Connolly, said.

Duarte, however, has labeled Hitchins “basic” despite his consecutive victories over former 140lbs champions Liam Paro and George Kambosos Jnr, the latter being an eighth-round TKO.

“Saying I’m a basic fighter, if you look at my resume, [among] every guy I fought, nobody else had done that to them,” Hitchins argued at Thursday’s press conference. “I fought undefeated guys, beat a threat in Jose Zepeda, won the title versus Liam Paro, fought George Kambosos and annihilated him.

“This guy [Duarte] has been spoon-fed his entire career. He’s never fought a threat until his last fight [Kenneth Sims Jnr] and damn near lost that fight. He’s not fighting punchers; started off his career against guys with losing records. 

“He’ll find out Saturday night that there are levels to this, and that I’m far from a basic fighter. This is exactly what George Kambosos was saying, and he got in that ring and found out the hard way.”

Duarte was into button pressing, 

“I’m definitely going to apply pressure and come at this guy like a train,” Duarte said. “See you in the ring Saturday.”

Hitchins acted incredulous at Duarte’s belief he can win, claiming the train tactic is because of his limited fighting style.

“He has no choice – he has to do that,” Hitchins said. “He’s going to get knocked out like he did versus [Saturday main-event fighter Ryan] Garcia.

“With 20-0 and eight knockouts, people don’t think I have the power, but I’ve been fighting tough guys and he’s been putting hands on guys like Joseph Diaz Jnr. Him talking about knocking me out. I don’t know what this fool is talking about. I’ve never been down in my whole career. He’s not going to be the guy to do it.”