Famed neuropathologist Bennet Omalu -- the inspiration for the Will Smith "Concussion" movie -- tells TMZ Sports ... Tua Tagovailoa should never play another down in the NFL again after suffering a scary head injury last week.
"If you love your life," Omalu said in a message to the Miami star, "if you love your family, you love your kids -- if you have kids -- it's time to gallantly walk away. Go find something else to do."
Tagovailoa was injured in the second quarter of the Dolphins' loss to the Bengals last Thursday .