I have been involved with youth sports and concussions. Sometimes a kid takes a big hit to the head and no concussion and other times a kid doesn't appear to have taken a hit to the head and the kid has a concussion. My point is that you can not tell if someone will get a concussion from the incident, but you have to rely on the symptoms and have a doctor do the diagnosis. When in doubt, sit them out. From my experience, if a kid can sit on the bench after the incident, the kid probably doesn't have a bad concussion.