That's 28-year-old UFC fighter Marlon "Chito" Vera opening up a verbal can of whoop-ass on Suga Sean ... 4 months after handing O'Malley the 1st loss of his career.

Remember, Vera won by TKO in the first round after O'Malley suffered an apparent ankle injury early in the fight.

After the loss, O'Malley wasn't exactly complimentary of his opponent -- saying, "I lost to a guy I feel like is not that good."

O'Malley also recently posted a photo of him punching Vera with the caption ... "Unbeaten."

These guys hate each other's guts ... so, rematch??

Very unlikely, according to Vera, who tells TMZ Sports he's got bigger fish to fry.

"Let's be real. There's not big money in the rematch because first thing, he's not Conor McGregor. Conor McGregor and Nate Diaz, that's money," Vera says.

"Whoever fights Conor McGregor, it's money! O'Malley is just like a lower version of Conor McGregor. He's like the China version of him -- he's made in China. He's fake!"

Despite the trash talk, Vera says if UFC honcho Dana White offered him the fight, he wouldn't turn it down.

"Don't get me wrong, Dana White told me, 'You never refuse a fight.' They know I never refuse a fight, so if they call me one day to fight him or somebody else, I'd take it!"

Music to the ears of fans who want to see these dudes back in a locked cage together. But first, Vera has his hands full next weekend at UFC Fight Night 183 with MMA legend Jose Aldo.

"[Aldo's] definitely a killer. He's definitely a tough fighter, but of course, I definitely believe his time has passed."