Whenever I read comments regarding the evaluation of a player defensively, the only references are +/- plays and errors. So, am I to assume that if none of those defensive notations occur, that any player would have made the play? I was looking at several teams who use, as an example, A+/D- first basemen, who commonly make an incredibly low number of errors, and less than 10 - plays. Would I be correct in assuming that the 10 - plays are all I am losing from using this player, or would, say, a B or C range 1st baseman get to batted balls and/or throws that don't show up? And then, of course, would this hold true for the other eight positions as well?

That's all there is in terms of +/- plays. Other than the fact that a guy with A range is going to make some + plays, that's it. They make all of the same single-out plays.

However, there is some kind of penalty associated with double plays. Nobody knows what it is. But in the infield, guys with bad range are also going to have an impact on your DPs.