Who is a replacement level player? How does one become defined as such? This article sheds some light on those questions. Replacement level players that are currently on major league rosters are listed too. Yes- there are some Astros on there. In fact, third base is populated by a bevy of onetime/former/current Astros: Mike Costanzo, Jose Castillo, and Geoff Blum. How far off is Aaron Boone from joining them? Probably not that far at all, sadly.