49ers ex-linebacker Chris Borland salutes Pat Tillman
Chris Borland retires from 49ers after one year due to fears over head trauma, NFL
NFL: Players call it quits in prime of careers
Chris Borland's Retirement Will Trigger Player Debate On Risk Of Future Dementia
SF's Borland quits over safety issues - ABC7 San Francisco
Denver Broncos: David Bruton retires from NFL after 8 seasons
Early retirement: Willis called it quits in his prime
San Francisco 49ers Chris Borland retires over repeated head trauma
Hanging it up: More NFL players quitting in prime of their careers
Hard Truth On Wisconsin Magazine
NFL: Early retirements over health fears may have ripple effect
Chris Borland Retires from NFL at Age 24: Latest Details, Comments and Reaction, News, Scores, Highlights, Stats, and Rumors