Next comes the fun part. We want to first release all players from all the teams and put them in the free agent market. We can do this from the FUNCTION menu under game setup.
Once you do that, you now get to become the serial killer you always wanted to be. Let's sweep the evidence under the rug first. Erase all career stats of all the players and then erase the entire league history.
Then move to the Free Agent screen and delete all of the free agents. Now the league will be empty.
The final step is to assign fictional players to all of the teams. This needs to be done for each league you have. MLB, AAA, AA, etc. If you want, you could change the modifiers for the creation of the AAA league to be lower than the major leagues, but since you are not going to be managing a team for 68 years, it really does not matter.
