An MLS soccer coach is learning the hard way ... DON'T SING ALONG WITH SONGS THAT FEATURE THE N-WORD!!
FC Cincinnati head coach Ron Jans just resigned after a player complained he used the N-word out loud in the team's locker room.
The player filed the complaint with the Major League Soccer Players Association -- which notified FC Cincinnati team officials ... and an investigation was conducted.
Jans has admitted he used the N-word in the locker room but insists he wasn't trying to attack anyone ... he was simply singing along with a song that was playing.