World Cup fans may seem crazed, but it’s the players who should have their heads examined. A review found that concussions due to heading the ball affected up to 9% of all injuries during games—disturbing, as heading is one of the very basic skills of the game. Basic—but not benign: Recently, an autopsy on MLS player Patrick Grange, who died in 2012 at age 29, found stage-2 CTE, a degenerative brain disease linked to concussions, making him the first soccer player named to have it. Says MLS medical coordinator John Gallucci Jr. in his brand-new book, Soccer Injury Prevention and Treatment (out this month), “Parents, coaches, and players all need to recognize that a concussion isn’t like any other injury. It is a traumatic brain injury that can…potentially be harmful to daily living by affecting the way we think, feel, and move.” Just a heads up.