The postseason roster date is slowly approaching in one of my worlds and I'm thinking of calling up one of my better infield prospects to shore up my infield depth for the stretch run and postseason. My offense is a little thin right now because of some injuries and I want to be sure that I have a good option off the bench should another player go down, and plus the guys is a good runner that could come in useful for pinch running. However, to be realistic he probably wouldn't have a starting position on my squad next year. So I have three questions:
1. If a player on the 60-day DL isn't scheduled to be healed until the middle of the first round (even though I might have a bye) is he worth activating?
2. If there is an injury to someone on my postseason roster after the deadline, am I SOL or can I call someone up to replace him on the roster?
3. Do playoff games count against a players service time?

You can add/remove players only between playoff series.

No, playoff games do not count against ST.  

So say I had a bye in the first round, once the first round was over could I add a couple of players even though my team would not have played a postseason game yet?

Yes.  As long as you do it after your opponent's series ends and before your series starts. 

Keep in mind that any player you're going to add has to be on the 40 at roster expansion.  Doesn't have to play in the bigs but must have been on the 40.

Great this helps a lot, thanks.