Some real talk from UFC rising star Sean O'Malley ... who tells TMZ Sports he's a BIG fan of Wiz Khalifa, but knows the dude would get crushed if he took a real UFC fight.
Remember, Wiz has been training like crazy at Jay Glazer's Unbreakable gym -- and even UFC champ Tyron Woodley says he's been very impressed with the rapper's fighting skills.
In fact, Wiz told us he believes he could compete in a pro MMA fight -- but won't do it unless someone offers a TON of cash.