Wow. First and foremost, great goal by Florenzi - perfect execution.
Secondly...
As far as I can remember, football is a team sport. It's incredible how many people are calling Ter Stegen the sole reason that Barca didn't win. Scapegoat much? How about MSN create some more chances and executing them instead of messing up? You see, this goes both ways. Stop being a bunch of hypocrites. You have one of the most talented goalkeepers of this generation. If you don't want him, please know that many other top teams won't hesitate pursuing his talents. Patience goes a long way in the development of a world class talent.
Players make mistakes, but just because they do it doesn't mean they're bad. I'd advise removing the sand from your vagina if you're honestly distraught by the thought of having Ter Stegen be the future nr1 at your prestigious club.
Let's rather focus on the fact that it was an incredible shot and Ter Stegen made an error of judgement, one that I think would have been shared between numerous other top class goalkeepers.