Tua Tagovailoa is now dealing with the third diagnosed concussion of his NFL career, all of them coming in the last two seasons.And there are now questions about his future — both short-term and long-term.The Miami Dolphins quarterback was hurt in his team’s 31-10 loss to the Buffalo Bills on Thursday night, sustaining the injury on a play where he collided into Bills defensive back Damar Hamlin. Tagovailoa, who was rushing successfully for a first down, initiated the contact by lowering his shoulder into Hamlin instead of sliding as many quarterbacks do on a scramble.Players from both teams immediately began gesturing that Tagovailoa needed medical attention as he lay on the turf and exhibited some signs typically associated with a traumatic brain injury. He remained down on the field for a couple of minutes, got to his feet and walked to the sideline after the play in the third quarter.He …