Not one to shy away from an odd conspiracy theory or two I'd proffer my version of events and we'll see if they pan out...
I say the coach noticed a player was tanking the game and he confronted him in his hotel room after the match and threatened to out the player. At this point a scuffle broke out and the player in question strangled him. It would take someone with some pretty good upper body strength to strangulate someone to the point of breaking their neck, ie an athlete.