Why not just preventing the users to set a lineup where all the selected players have not a position...?
@JoeMaverick and other: Because we already have lot's of default lineups set that way. We'd have to fill them automatically which is not something users would like (forcing something on them). Also, I believe more resourceful users would find a way around it somehow... But, I will give it some more thought, maybe there's a way to make sure.
@Yuck: No worries, I love to hear opinions, even if they don't align with mine. And no, you haven't been a hindrance, just a part of a discussion. As for the test sample, I see your point and will probably do it at one point, but for now, I'd like everyone to just use a completely blank lineup one week, and then a completely full one the next, LCD. Doesn't have to be in that order. Having two private league matches is a very complicated, so not an option.