The ref really should of stopped the game on Arsenal's first equaliser. That's the mandate now isn't it? Any head injury and play gets stopped immediately? Big clash of heads. Giroud down for the count. Sakho stumbling around seeing stars. What more do you need? The fact Sakho didn't do the smart thing and go to ground like Giroud shouldn't come into it.
Not so much bothered it was allowed to stand as the subsequent defending and goalkeeping was real poor. (Although Sakho was a part of that.).
Just continues to be disturbing how officials STILL aren't IMMEDIATELY stopping the game when there's a threat of a head injury and concussion after a clash like that. To not put too finer point on it, football, as much as they say the right things on the concussion issue; are a sport that continues to put players lives at risk out on the field.
It was in the final third, no ref will stop the game at that moment. If they do then defenders will always use that as a tactic to defend when they lose the header in final third. Just collapse for few seconds, ref will stop immediately and then game restarts.