Teams can be picked just once through the contest. It follows similar rules to NFL survivor pool where you can only pick a team once. 

Please check [ the post where I wrote the rules](https://stacker.news/items/894320). Also I mentioned  [some additions following discussions with @Undisciplined](https://stacker.news/items/901987)

This means, in your case,  that you have used Real Madrid once and can not be chosen again. 

Carresan

If I still choose Real Madrid next time, and they play a 1-2, 2-3, or 0-1 match against Atlético Madrid, the aggregate score will be tied since Madrid won the first leg 2-1. The game will then go to extra time or penalties, where Real Madrid could either win or lose.
At that point, what will be the outcome of my prediction?

Stacker_Sports

UEFA Champions League Survivor Pool: Week 1 recap

If I still choose Real Madrid next time, and they play a 1-2, 2-3, or 0-1 match against Atlético Madrid, the aggregate score will be tied since Madrid won the first leg 2-1. The game will then go to extra time or penalties, where Real Madrid could either win or lose.
At that point, what will be the outcome of my prediction?

