The roster as of midnight on August 31 will determine who is eligible for the playoffs.
All players on the 25-man roster are eligible
All players on the 15-day DL are eligible
So, the current roster (which I understand may still change before the deadline) is eligible in addition to Bruney, Floyd, Septimo, Hudson, and De Aza. However, Bruney may get moved to the 60DL which would make him ineligible (not that he would be considered anyway).
Anybody who remains on or goes on the 15DL through the end of the season can be replaced by somebody not already eligible.