Hamlin collapsed on the field during the first quarter of the nationally televised game against the Cincinnati Bengals and was given medical treatment for nearly 20 minutes before being taken to a hospital.
"Damar Hamlin suffered a cardiac arrest following a hit in our game versus the Bengals. His heartbeat was restored on the field and he was transferred to the UC Medical Center for further testing and treatment," the Bills said in a statement. "He is currently sedated and listed in critical condition."
Jordon Rooney, a family representative who described himself as a good friend of the player, told ABC's "Good Morning America" on Tuesday that Hamlin's relatives are in good spirits but going through a lot and need their privacy.