One of your players stayed downfield too long, and was hit in the head at close range by a goal kick. He seems to be okay, but it's hard for me to tell at such a great distance.
If a player is not expecting to be hit by the ball, so has not stiffened his body sufficiently, it is possible for a well-kicked ball traveling at high speed to cause a concussion. A player should be carefully checked after an impact like this to ensure that it's okay for him to continue playing.
There is still a lot of controversy about whether ball impacts are dangerous, either acutely or chronically. Many recent studies agree that if a player is prepared for ball contact and heads the ball properly, there is very little chance that he will be concussed, so heading in general is probably okay if it is done properly. There are conflicting opinions about whether a lot of these sub-concussive blows can cause long-term cognitive deficits. Some studies have claimed to find links between soccer heading and late-life depression, Alzheimer's disease, and Parkinson's disease, but others dispute these findings. There is currently no conclusive evidence whether frequent heading can lead to eventual brain damage or not.
That's a judgment call. Heading is an integral part of soccer; if heading were outlawed the game would lose a large part of its attractiveness. A well-directed header goal off a corner kick is exciting. Without heading soccer would be a completely different game. Add to that the fact that proper heading very seldom causes a concussion, and you have a strong argument to continue to allow heading until there is a proven reason to ban it. But care should be taken to train players to head properly. Also, many experts suggest that heading should not be allowed until players reach a certain age - perhaps twelve years.
