At the main menu, go to "My Madden" then to "Create-A-Player". Create them however desired, but set what team you want to be on in Superstar mode and make them a rookie. When you go to "Player Rating", choose "Create Custom". You can now make your player as good or bad as desired. Exit the Create-A-Player mode. If you do not want to change your default rosters, choose the "Keep player without saving" option. Then, go to "Game Modes" and select "Superstar". Then, select "New Superstar" and choose the "Play as Rookie" option. Find your created person under the list of players. This will give you control of the Superstar at the start of preseason, and he will be exactly the same that as he was when you created him. This works well if you are bad at the mini-games and cannot get a good player normally.