The last time the Broncos returned a kickoff for a touchdown feels like ancient history. Trindon Holliday, a 5-foot-5 mighty mite, ran 105 yards through a crowd of head-hunting Philadelphia Eagles defenders from deep in his end zone to the other coast in 2013. There were, amazingly, two kickoff returns longer than Holliday’s that season, a 109-yarder and another for 108. Fans may never see it again. If the NFL has its way, the return will go the way of leather helmets and a coach’s fedora, a relic of a long-ago game.