Kelvin Gastelum Channels 'Rocky 4,' Says He's Gonna Rip Whittaker's Head Off

Rocky fought Drago in the Soviet Union ... and Kelvin Gastelum's fighting Robert Whittaker in Australia -- and just like "Rocky IV," Gastelum says he's gonna beat the hell outta the home-country hero.

TMZ Sports talked to Gastelum -- whose favorite boxer is Rocky Balboa (yes, we all know he's a fictional character) -- days before fighting Whittaker, the UFC middleweight champ ... in his home country.

Gastelum lives in California ... and traveled 8,000 miles for this fight. So, he's expecting everyone on the continent to be rooting against him.

Sounds a lot like "Rocky IV" ... but Kelvin says he ain't worried.

"It's all good. Look what happens at the end. Rocky turns everybody over on his side, and he wins the fight."

Gastelum says that's precisely what he's gonna do ... but instead of a crushing knockout blow, he's gonna "rip his head off" and take his belt.

"I plan on taking that 12 pounds of gold. It's a long flight home. I don't plan on going empty-handed."