Vin Diesel Says He'd Beat The Rock Down In REAL Fight

If Vin Diesel and The Rock came to blows, Vin is adamant he'd whoop Rock's candy ass all the way back to the WWE ... and he's serious.

Just ask UFC champ Tyron Woodley -- who says he was confronted by Vin (in a non-violent way) at the "Guardians of the Galaxy Vol. 2" premiere because Tyron publicly picked Rock to win in a hypothetical cage match.

Woodley explained the whole thing on the "TMZ Sports" TV show on FS1 -- saying Vin "pulled up" on him at the premiere and explained why he'd kick that ass.

We're told Vin cited his experience as a bouncer back in the day before he was a movie star.

There was bad blood between Rock and Vin when they were shooting the last installment of 'Fast and the Furious' ... but they've squashed the beef.