UFC's Paige VanZant -- You're No Ronda Rousey ... Says UFC Champ

She's coming off the biggest win of her career ... but UFC's new rising female superstar Paige VanZant would get MURDERED in a fight with Ronda Rousey ... so says UFC stud Demetrious Johnson.

Johnson -- the reigning flyweight champ -- says VanZant COULD be the next great female fighter ... but don't go crowning her just yet.

FYI -- 21-year-old VanZant extended her UFC record to 2-0 this weekend with a DOMINATING performance at "UFC on FOX 15" this weekend.

Clearly, Johnson doesn't think VanZant stands a chance against Rousey in the octagon ... but there is one arena he'd like to see them compete.

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