The National Football League is once again facing scrutiny over its policy on traumatic brain injuries and concussions, following a series of high-profile head injuries this season. On Thursday evening, Indianapolis Colts running back Nyheim Hines was pulled from a game against the Denver Broncos after he struggled to get to his feet after he was struck in the head. This comes after Miami Dolphins quarterback Tua Tagovailoa suffered a horrifying concussion in a game against the Cincinnati Bengals in September. This week, the neuropathologist Dr. Bennet Omalu, whose work was depicted in the 2015 film “Concussion,” said the 24-year-old star should retire from football.