former players have been diagnosed with chronic traumatic enselfa losify, a disease caused by concussions and other form of head injuries, and the symptoms range for erratic moves and behaviour. it can only be detected after death. ryan was the first to be diagnosed. on average, how much concussions occur over the course of a year? >> we have between 20-30 a year. there's about 750 players. that's not a lot when we look at it. despite it infree questionsly, major league has been working urgently. dr gary green is the director of medical services. >> when did the league become seriously worried or concerned about. in the last 5-6 years, baseball is concerned. over the last four years, new equipment and information has been implemented. instituting a 7-day disabled list, allowing players adequate time to heal. >> we did a study in 2010. >> if a player had a concussion, you wouldn't put them on a disabled list. you'd lose him for eight days, list. >> reporter: what do you think the lesson of ryan's death should be. >> should be to the public, and should be that concussion matters, it creates