Basically you have Team and Players. You need to define a player, but the players data comes from a Team.
In my form class i have
team = forms.ModelChoiceField(queryset=Team.objects.all()
player = forms.ChoiceField()
Select a valid choice. 2 is not one of the available choices.
Ordered by complexity DESC:
choices = Player.objects.values_list('id', flat=True)
CharField, but render it manually in template as select box.