And now it is Frazier who appears to have the next crack in this game of musical chairs among three black American fighters -- Ali, Frazier and Foreman. Their only potential threats on the horizon are Teofilo Stevenson, a Cuban giant whom Fidel Castro may not permit to leave home, and Duane Bobick, an American Olympian such as Ali and Foreman who is now unbeaten as a pro.