4:25 PM PT -- XXXTentacion's Thursday night concert in Santa Ana, CA has been postponed. We're told the venue decided to postpone for safety concerns, on the heels of Wednesday's brawl. The show will be rescheduled.

The guy who KO'd XXXTentacion at his San Diego show is just jealous of the 19-year-old rapper's success ... and XXX believes there's NO reason to hire more bodyguards.

We spoke to him Thursday after the brutal cheap shot. Although his face seemed pretty swollen, XXX says his attacker got it worse. In the video, you can see security beat the living daylights out of the guy.

Still, police tell us the suspect somehow manged to flee the scene.

According to XXX, his attacker got past 12 security guards to get to him -- which, to him, means there's no point in paying more people to protect him.

One person was stabbed backstage. At the time we spoke to him, XXX thought that person was the attacker. Cops tell us that's not the case and the stabbing victim's injury is non-life threatening.

Cops still haven't named a suspect, and there's no evidence another rapper, Rob Stone, had anything to do with it -- despite an old beef with XXX, and the chants of fans after the fight.