The Game is being sued for that punch he threw last month during a basketball game ... a punch the victim says may have screwed up his brain.
According to a lawsuit filed Monday, Onyebuchi Awaji -- an off-duty rookie cop -- claims he did nothing to instigate the March 29th fight with Game.
Awaji claims Game nailed him with a sucker punch that may have caused brain damage.
Not only did Awaji claim Game sucker punched him, he says Game fled the scene as soon as he heard cops were called.
At the time of the fight, sources close to Game told TMZ Game threw the punch out of self-defense, claiming Awaji verbally threatened Game with a gun.