TMZ has obtained demand letters fired off to the 2 rappers on behalf of a budding Australian soccer star, who claims his career has been sidelined because of the beating.

Nelly Yoa says back in January 2015, Dolla and YG physically assaulted him at Eve Nightclub in Melbourne. As TMZ reported, Yoa claims he was in the VIP area when the rappers and their crew rolled in and tried to shove everyone else out. Yoa refused, and says Dollar and YG began punching and kicking him in the head.

According to the demand letter, Yoa suffered physical and mental injuries, which has prevented him from earning what he says would have been a "substantial income." He says he lost a prospective soccer deal with the Melbourne City Football Club.

The letter is a formality which must be sent before a lawsuit is filed.

We reached out to Dolla and YG ... so far, no word back.