Start a season. Select the "Cheats" option at the seasons main menu. Enter one of the following codes to unlock an All-Star player to place on your team.
BAMSTAR
GOCIRCUIT
BESTBUYSTR
TARGETPLYR
EBRULES
TOYSRUSCOM
SIKPOWER
SIKSTAR
GAMESTOP
MLB teams:
Start a season. Select the "Cheats" option at the seasons main menu. Enter ILUVMLB as a code.
