TMZ Sports talked to Chimaev ... and asked if he'd fight Adesanya or Costa this weekend in Abu Dhabi if either of the men were unable to participate in the UFC 253 main event.

That might sound crazy ... until you consider the 26-year-old undefeated fighter fought and won twice -- only 10 days apart -- back in July.

Khamzat's answer? Well, you probably already know.

"Yes, 100%, I'm ready," Chimaev said.

"Of course, 100%, for the title, I'm always ready. I would be so happy to be given the chance to jump in there. 100% gonna take this."

Chimaev -- who has been hit a grand total of 2 times during his 3 UFC fights -- also laid out his hit list ... the guys he wouldn't mind beating down while he pursues the UFC strap.

"My dream is title, but I can fight with everybody. Demian Maia, Jorge Masvidal, Diaz brothers, Conor McGregor, everybody, everybody, I can smash everybody. Doesn't matter."

Then, Khamzat threw one more dagger at The Notorious ... the guy who once called him "rat lip."

"People talk about him, Khabib smashed him, brother. Already, everybody knows what I'm about. [Conor's] not on my level. Khabib showed that to everybody."

"It's gonna be the same. I take him down and smash his face."