Seven former players have sued the NFL in Philadelphia over the league’s handling of concussion-related injuries, the first potential class-action lawsuit of its kind. The players accuse the league of training players to lead with their heads, failing to properly treat them for concussions and trying to conceal any links between football and brain injuries. The plaintiffs include two-time Super Bowl champion Jim McMahon, who has said he played through five concussions but now frequently walks around “in a daze.”