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 ... and Omalu, who discovered CTE, said from everything he saw on the game's broadcast, he believes the quarterback "suffered severe, long-term permanent brain damage" during the play.
Very scary as Tua Tagavailoa goes down after a sack, looks like it may have been the second concussion in 4 days. Really not good. pic.twitter.com/2u0Leb69O5