LaMelo Ball was anything but mellow during his JBA international matchup on Monday -- SLAPPING his opponent and starting a BRAWL before getting ejected!!
The youngest Ball's Team USA squad was facing Alytaus Dzukija in Lithuania (welcome back) ... when Melo and his opponent got physical in the 3rd quarter ... and Melo hit him with a slap that would make Nate Diaz proud!!
Both benches cleared ... and all the players -- including Melo's older brother, LiAngelo -- had to be separated from the other teams.
Team USA ended up losing 124-116 ... and we're sure LaVar would say it's 'cause Melo wasn't in there for the last part of the game.