One of Jussie Smollett's alleged "attackers" is on a roll -- shortly after starring in his first movie ... he's hanging out with one of the biggest celeb athletes in the world.
Abel Osundairo met up with Floyd Mayweather this weekend at the undefeated fighter's gym in Las Vegas ... then hit up his club later on for more face time with the boxing champ.
We broke the story ... Abel's been training with Floyd's renowned trainer, Nate "The Snake" Jones, in order to advance his own promising boxing career after winning a title in Chicago's Golden Gloves tourney in April -- a fight that wasn't staged!