Hawkins, who had shared his intentions with the Patriots, relayed the reason for his decision on Uninterrupted, the network developed by LeBron James and his business partner and CEO, Maverick Carter.
"After OTAs and through summer training, my body just didn't respond and wasn't feeling the way it should going into camp," the 31-year-old Hawkins said. "Basically it just started breaking down on me."
The Concussion Legacy Foundation says Hawkins has pledged his brain for research into chronic traumatic encephalopathy, or CTE. The degenerative disease is known to cause cognitive and behavioral problems in athletes, members of the military and others who sustained repeated head trauma.
Hawkins was trying to crack a crowded wide receiver depth chart, with Julian Edelman, Brandin Cooks, Chris Hogan, Malcolm Mitchell and Danny Amendola at the top, and was considered a bubble player to make the roster.
Hawkins said it was a "tough call" and "bittersweet," relaying that he is pursuing a Ph.D. in business and economics. He had made headlines in the offseason by earning his master's degree from Columbia with a 4.0 GPA.
Information from The Associated Press was used in this report.