Complex django annotation

Question

I have the following models:-

class Group(models.Model):
    name = models.CharField(max_length=200)


class Game(models.Model):
    group = models.ForeignKey(Group, related_name='games')
    date = models.DateField()
    players = models.ManyToManyField(
        Player, through='GameMembership', related_name='games'
    )


class GameMembership(models.Model):
    game = models.ForeignKey(Game, related_name='memberships')
    player = models.ForeignKey(Player, related_name='memberships')
    selected = models.BooleanField(default=False)
    injured = models.BooleanField(default=False)


class Player(models.Model):
    group = models.ForeignKey('groups.Group', related_name='players')
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='players')

I want to annotate all of the players in the group with a score which is calculated as follows:-

For the last 10 games for which a player wasn't injured, score 5 if they were selected.

I can do this using Sum/Case/When if I ignore the "wasn't injured" clause, by using a manager method on Player which looks something like this:-

def with_availability_scores(self, group):
    for_games = group.games.reverse()[:10]

    return self.annotate(
        availability_score=Sum(Case(
            When(
                memberships__selected=True, memberships__game__in=for_games,
                then=5)
            default=0, output_field=IntegerField()))
        )

But the addition of the "injured" clause means that I can't use that for_games variable like that to begin with.

I suspect it can be done using Subquery and OuterRef but I can't quite figure out the exact syntax I need.

Any ideas?