what are the central metaphor of in the play fences?

I think that baseball is a major metaphor in this play. In act 1 Troy states that, "Death ain't nothing but a fastball on the outside corner." Baseball thus becomes a metaphor for Troy's life. A home run comes to mean Troy's victories over seemingly insurmountable obstacles. Death is another metaphor that Troy uses. As tTroy ages he, like all of us, is closer to death. But age also separates him from baseball which was so integral to his life.