One morning in 2002, neuro-pathologist Dr. Bennet Omalu stood above his autopsy table and stared at the first brain he'd ever seen that belonged to an NFL player.
At the time he knew "practically nothing" about football, but was brimming with "intellectual curiosity" to understand what had led to the sad demise of Mike Webster, the legendary lineman on the table below him whose life fell apart after his retirement a decade earlier.
Since then, Omalu, who grew up in civil war-torn Nigeria, has learned plenty about football and – with the help of Webster's damaged brain – became the first physician make the connection between head injuries that players have endured and a nightmarish, degenerative brain disease now known as chronic traumatic encephalopathy [CTE].
"It took a foreigner who knew nothing about football to make this correlation," says Omalu, whose story is told in the feature film Concussion, starring Will Smith as Omalu.
After publishing the reports of his findings in 2005, he assumed the NFL would be interested in learning about the risks – which included depression, drug abuse and suicidal behavior – that "repeated sub-concussive blows to the head" posed for players.
Omalu, however, quickly realized that he was mistaken. The NFL spent years attacking his reputation, trying to discredit his research and demanding retraction when his findings became public.
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"They went after me, the messenger," says Omalu, who now works as the chief medical examiner for San Joaquin, Calif., and teaches at the University of California-Davis. "But I fought back."
The NFL eventually came around to embracing Omalu's findings. Last April the league agreed to settle a class action lawsuit to provide up to $5 million to any retired player with serious medical conditions linked to repeated head traumas.
"I'm not against football," insists Omalu, who was studied the brains of nearly 40 players and says "all but one" have tested positive for CTE. "I just think people need to know the risks involved."