GrafBelisarius
The tutorial says 18 active players must be available at all times. That's fine. What's not fine is my being blocked from releasing a player when that takes me down to 19 active players, with the message "You do not have enough backup for injured players." I do have enough backup.
EiPiX
You got 21 players, including 1 injured, 1 loaned in and 1 listed, which makes it's currently 18 "active" players.
If you remove the listed player for the transfermarkt or wait untill the other player is fit again, you could release a player.
GrafBelisarius
That's a strange way of figuring active players, but at least I can understand it. Thanks!