Because the game always do the simulation with 11 players, and if you leave your club, and players are retired, the game will add old players to the squad to complete the min. of 14 players.
Automatic defeat for 3-0 exist only in the case that you don't have 11 players to use, but no if there are 14 in the list and 11 or more to be used to play.
As I said, if the squad have 11 players to use, the game do the simulation with these 11.