UFC's Tyron Woodley Says The Rock Would Beat Vin Diesel's Ass

It's probably in Vin Diesel's best interest to squash the beef with The Rock asap -- 'cause Dwayne Johnson would whoop that ass if things came to blows ... so says UFC champ Tyron Woodley.

Woodley (who's also an actor) says he recently went to the "Fast 8" set -- and says he thought things seemed peaceful ... though Rock wasn't there at the time.

But that was then ... before Rock called out Diesel as an unprofessional "candy ass" on social media.