DARLINGTON, SC - SEPTEMBER 04: Dr. Micky Collins (R) of the University of Pittsburgh Medical Center Sports Medicine Concussion Program, speaks as Dale Earnhardt Jr. (L) and Rick Hendrick, owner of Hendrick Motorsports, listen during a press conference prior to the NASCAR Sprint Cup Series Bojangles' Southern 500 at Darlington Raceway on September 4, 2016 in Darlington, South Carolina. (Photo by Blaine Ohigashi/Getty Images)