UFC's Urijah Faber -- Mario Lopez Can Fight ... 'He's the Real Deal'

A.C. Slater's no bitch ... so says UFC superstar Urijah Faber who tells TMZ Sports when it comes to fighting, Mario Lopez is the REAL DEAL.

Faber says he and Lopez have been friends for a while -- and can personally vouch for his fighting skills ... saying Lopez really excels in boxing and wrestling. For real.

"Mario is a beast, brother."

The "Extra" host is 42 years old -- but Faber says the guy is in insane shape and could seriously hold his own if Dana White comes calling for a real deal UFC fight.

Zack Morris rematch, anyone???