By Zach Koons The union’s investigation into the handling of the quarterback’s head and neck injuries this week remains ongoing. NFL players association executive director DeMaurice Smith said the union plans to “pursue every legal option” as it continues its investigation into how the injury to Dolphins quarterback Tua Tagovailoa was handled over the last week. Smith sent a statement to two members of the Amazon broadcast team, Andrew Whitworth and Richard Sherman, after Tagovailoa left Thursday’s game against the Dolphins with a head and neck injury. His departure from the contest came just …