Didn't Van Dijk nudge Ramos into Karius? I'm sure Ramos would have taken the opportunity to use it to his advantage when it presented itself though.
I've not seen a particularly good video of the point of impact, only clips from some way off, so I have not seen exactly where the blow landed.
It didn't look a particularly severe blow to me though. If it resulted in concussion it was pure bad luck. At the time Karius showed no apparent ill effects. Got up immediately. He never lost consciousness. Seemed fully aware of his surroundings, was complaining to the ref immediately. Possible slight delayed reaction but he made other saves and correct decisions after and before the second Bale goal.
Maybe it was caused by the kicking the Liverpool players gave him in the changing room after tha match. ;-)
Still, it's nice for the victims to have an extra excuse.
Plenty of people can take elbow strikes. Most MMA fighters get worse than that every time they fight. Then there are those elbow strikes which may be slightly more vicious.
https://youtu.be/yEizMbUR3cE
https://youtu.be/Uh9l58GUZNc
https://youtu.be/RBpffwzl2_4
I love elbow strikes, one of my favourite techniques. Great for close quarters.