Holly Holm shocked the world when she KO'd Ronda Rousey, so you better believe she can slay Cris Cyborg -- so says UFC rising star Rose Namajunas.
"She's already proven that if she's the underdog, she can surprise people," Rose told TMZ Sports.
Namajunas would know ... she just starched Joanna Jedrzejczyk -- the most dominant fighter in the UFC since Rousey -- to win her first belt.
So when it comes to UFC 219's main event ... Rose says you should take Holly's head-kick to the bank.