Nipsey Hussle's former bodyguard went after The Game's manager during the rapper's set Sunday night ... apparently over some disrespectful comments made about Hussle.
Sources close to the situation tell TMZ ... Nip's bodyguard and close friend, J Roc, attacked Wack 100 backstage at the Rolling Loud Festival while The Game was performing.
We're told J Roc punched Wack several times in the face, then took off. Video of the aftermath shows an angry Wack having to be restrained from going after J Roc by venue security.
Wack's already responded to the incident by posting a video showing closeups of his face -- without any visible injuries -- and saying ... "Whooping Wacks ass takes more than words it takes a action !"
He adds ... "Next time you send a motherf***er, don't send one who knows how to run, send one who knows how to fight."
As for why there's bad blood between the late rapper's camp and The Game's ... it seemingly stems from Wack 100's recent comments about how Nipsey Hussle's not a legend. Wack told us it's nothing personal -- it's just about numbers ... and he doesn't think Hussle's stack up.
Game made it clear his manager doesn't speak for him, but regardless ... J Roc wanted to send Wack a message.