Frankie Delgado isn't quite the famous face he used to be, and cops had to step in when the former reality star tried to get through VIP at the Mayweather/McGregor fight.

The incident went down when the ex-'Hills' star tried breezing past security Saturday night outside the VIP entrance to T-Mobile Arena. Our law enforcement sources tell us Frankie tried to walk in without showing credentials, and ignored security's objections.

Witnesses tell us he never used the words, but his attitude reeked of "You know who I am."

A Las Vegas PD Sergeant stepped in to stop Frankie while security sorted out the matter. The tense moment was captured in this photo, and despite how it looks ... everything worked out for Frankie.

Someone eventually confirmed he was on the list, and he watched the fight from VIP.

Fun fact: Frankie's still A-list at huge events! We underestimated "The Hills."