Now you're just being dishonest. Most goalkeeping blunders can be attributed to concussions, because they almost always involve a lack of mental focus, poor co-ordination and slow reaction times. That doesn't mean you fit them to a concussion.
Rumours in the press do not constitute evidence of a concussion. And these very rumours don't even support your theory because the tests were taking after the game. So there's no way to know what caused the concussion IF it exists in the first place.
The final nail in the coffin is that Karius has made similar errors in other games, and unless he was concussed in those as well your concussed theory doesn't hold up to scrutiny.
To me it feels like you're going out of your way, to create unlikely scenarios, instead of accepting that what most likely (not certainly) happened is exactly what I have described. Ramos and Karius had contact. That contact was of a nature forcible enough, to cause a concussion. Shortly thereafter, Karius had two extreme blunders in his game. The first one being so bizarre, that it was even extremely unlike for someone as prone to errors like Karius, to commit it. Then he had another bad one. So you have one blunder so bad, most goalkeepers don't have a single one like that for their whole career and another bad one, in the same game. Even for someone like Karius, that is highly unlikely to happen under normal circumstances.
Shortly after the game, the first rumors of a possible concussion made the rounds. Now a paper with a history of getting access to intimate details, with a history of even receiving information directly from the people involved, especially when it comes to sports, reports, that the team suspected him of a concussion. They claim, the team sent him to an expert, who ran multiple tests with him, the majority of which indicated a concussion. Therefor, it is extremely likely that he had just that: a concussion.
The symptoms of a concussion are many. Generally, a persons brain functions are affected, to varying degrees. Also a persons balance and concentration are affected. A person might experience (or is likely to have) a feeling of confusion, dizziness or fatigue.
Now you could collect the dots and create the following narrative:
He got concussed early in the game, most likely when he and Ramos had contact. He then suffered typical symptoms from a concussion, possibly without even realizing, that he is indeed concussed. Due to those symptoms, he caused the two blunders, which were even extremely unlikely for someone like him. After the game, he started to feel more symptoms, pr the symptoms got worse, or the docs got suspicious and he got checked up. He was then thought to be concussed, sent to Boston to be sure and the suspicion got affirmed. He is concussed. Due to leaks in the club, or on purpose, Bild got a hold of the information (which happens all the time).
What you are suggesting is, that he might very well had the worst game of his life and through coincidence, got concussed later. While that is possible, wouldn't you say that it is highly likely the first version, or a form thereof is true? And if so, shouldn't that absolve him from criticism, as he was injured, after all?