Chris Borland Retires at Age 24 Over Concussions
NFL star Chris Borland quits over head injury concerns - CBS News
49ers ex-linebacker Chris Borland salutes Pat Tillman
Concussions cause Bills rookie linebacker A.J. Tarpley to retire
49ers linebacker Chris Borland retiring at 24 due to long-term health
San Francisco 49ers' Chris Borland reveals a concussion during
Michigan football player quits over concussion concerns
Chris Borland retires from 49ers after one year due to fears over
Ex-49er Chris Borland still asked why he quit — and he keeps
Is Chris Borland an outlier or the start of a trend? With