[Gambo]

Basically all you would need to do is edit the master.csv and remove the player id (eg mattido01) from the players line.

Do you have any experience with excel?

I can give you a quick rundown of how to do it quickly if so.
1. Make a copy of the fielding.csv and open it and sort by team.
2. Delete the lines that aren't that team. You now have a list of all the players from a team.

Here's the excel experience.
3. Open the master.csv and copy the playerid into one of the unused columns (such as lahman or retro)
4. Create a blank column.
5. Do a vlookup formula to the fielding file to see if the player exists there
6. Save the master.csv and reopen and sort by your new column.
7. Delete the player ids for those guys you dont want.
8. Delete the column you created.
9. Save

You now have a master.csv that the game will only read those guys you want to use without any permanent loss if info. (If you want to add someone later put their Id back

Remove the .odb file from the directory and your good to go..