According to Nick Piecoro on Twitter:
Dbacks announce broadcaster Mark Grace is taking an "indefinite leave of absence to seek personal assistance."
More from Dbacks' release: "Due to the nature of Grace's request, the team will have no further comment on the matter at this time."
Maybe he got tired of working with Greg. Things cant be too exciting in the booth calling games with him. I wonder who is going to fill in now....maybe Gonzo?