https://www.sportscasting.com/nfl-concussion-protocol-explained-how-does-it-work/
During every NFL game, spotters watch the players on the field. A few will be on the sidelines, and a few will watch in a booth from above. If they spot anything suspicious with a play or athlete, they call a timeout. Someone will escort the person off the field to receive an evaluation.
In addition to the spotters, each team has an assigned neurotrauma expert who monitors players from the sidelines. They help monitor and evaluate a player’s condition. Some signs this team looks for are loss of balance and loss of consciousness after a hit. They watch for signs of confusion, disorientation, head clutching, facial injuries, and slow movements following a hard-hitting play.
Whenever they spot these signs, the player will go to the medical tent, locker room, or hospital for further evaluation. That’s when the concussion protocol goes into effect for the athlete.