San Francisco 49ers Chris Borland Retiring at 24, News
49ers LB Chris Borland retiring over concussion concerns
What It Means to Leave Football Early - WSJ
Chris Borland's NFL Retirement Cost Him Millions, But Could Add 2
Concussion Concern: LB Retires After One NFL Season
Chris Borland retires from NFL at just 24 years old, makes his own
Fearing brain injury, 49ers' Chris Borland retires after one year
Lowell Cohn: Chris Borland's retirement a choice to admire
Q&A with Chris Borland on the future of football, brain injuries and
SF's Borland quits over safety issues - ABC7 San Francisco
Chris Borland retires: The NFL's troubling CTE comments - Sports
Chris Borland's Concussion Concerns, Retirement Are Latest Big
Chris Borland retires from NFL aged 24
Chris Borland Retires from NFL at Age 24: Latest Details, Comments
24-year-old NFL player quits over concussion worries