All right here is what I think I understand:
1) 25 man roster that is set based on the 25 men on the roster Aug 31st
2) 4 extra pitchers to replace the 4 pitchers we have on the 60 day DL

So, if I understand this correctly, do we need to call up Denorfia by the 31st for him to be on the playoff roster? If so, can we use call him up and send down a reliever with options, say Belisle, Bray or Coffey and then add them back the next day when the rosters expand (the 31st is an off day). Whoever we send down would still be on the playoff roster using one of the exemptions.

Now for the next question, can we call up Homer in September and place him on the postseason roster using one of the exemptions for the 60 day DL even though he hasn't been up here all year. I'm not saying I want to call him up I'm just trying to understand our options.

And finally, when we make the playoffs, do we choose 25 men at the start of each series and the other four are inactive for the entire series? Please help me out and correct me if I'm wrong. I've seen a lot of things thrown out around here that seem contradictory or confusing.