We did everything wrong. #1 characteristic of Atletico is that they do not want the ball. They want you to have the ball in areas where they can pinch it and counter. And so we just walked into those areas for the entire 90 minutes. It just so happens that we like to have aimless possession in the areas where Atletico would prefer, so our styles match up in a very bad way.
They do everything to keep the other team from possessing the ball in between the lines of their midfield and defence. And guess what, we never touch it there even against Serie A minnows anyways, so it's perfect for them.
The best thing we could have done was punt them the ball on the opening kick off and play on the counter ourselves. This is the only way to get them to open up the space between their midfield and defence. Sadly that option no longer exists once they score on you.