Hernandez committed suicide in his jail cell in April at the age of 28 following his 2015 conviction in the murder of Odin Lloyd.
Baez indicated that the Hernandez family intends to sue the NFL and the Patriots, on behalf of Hernandez's daughter. The University of Florida, where Hernandez played in college, also later could be added to the suit.
An NFL spokesman said the league has not seen a copy of the suit and "cannot comment at this time."
Boston University's Chronic Traumatic Encephalopathy Center is perhaps the leading research center for the disease, often found in people who have suffered repeated head trauma, such as football players. The degenerative brain disease currently only can be diagnosed post mortem, when brain tissue can be examined on a cellular level.