I’ve seen a few sportsmanship related videos on YouTube where a soccer player will kick the ball, unintentionally of course, in such a way that it conks the ball boy, or the camera operator, or a fan, or whatever, right on the noggin. The respectful player will make sure the injured party is ok, apologize, and sometimes give them the ball or their shirt or whatever.
How often does this type of thing happen in a professional soccer league (your choice: MLS, EPL, La Liga, etc.)? A few times per match day? A few times per season? And also, are the injuries ever severe, like a concussion?
I get that my thread title doesn’t rule out fans and other personnel injured in fan violence. So I’m going to rule that out here, in the OP.
I have been watching Bundesliga, UEFA cup games, WC and Euros for more than 50 years, thousands of games, and I can only remember very few incidents like that, and none that led to serious injuries. It’s exceptionally rare. For comparison, I also watch a lot of tennis (but much less than football), and a lines ref or ball child getting hit is much more common than in football, sometimes with serious consequences, even fatal. I didn’t witness it, but it was reported at the time that a young Stefan Edberg accidentally killed a lines umpire this way.