NSA courtesy runner

[Little Jimmy]

I recently started doing some NSA tourneys and have a question. Rulebook says "the player in the batting order where the last out was recorded or any player not currently in the game may replace" etc., etc. My question deals with the second part of that sentence. "Player not currently in the game" means... a player that has NEVER been in the game (like FED and ASA) or a player who has been in the game but has been subbed for and is now not CURRENTLY in the game? The book doesn't seem to elaborate and I don't have a NSA umpire manual (if there is one). Any ideas? Thanks.