For a few years, my wife has been following the research into brain injuries that can be caused by bouncing soccer balls off of the head, that has resulted in the push to end the practice in schools, or have a requirement for helmets. The photo at this link to the local paper is from a couple of days ago.
These two high school girls are butting heads, with the soccer ball providing some relief from the impact, but if there’s a case for wearing helmets while playing soccer, this is it. One of the girls must have a knee injury, because if you click the link to the article you can see that she’s wearing a brace. So it’s doubtful she should have been in the game at all.