49ers Wunderkind Retires After 1 Year, Brings Concussion Issue Again to Fore
Chris Borland stuns 49ers with retirement announcement
49ers' Chris Borland, 24, quits NFL over concussion worries
49ers Linebacker Quits After 1 Season, Citing Safety Concerns : The Two-Way : NPR
Chris Borland's Early NFL Exit Doesn't Mean Avoiding Brain Damage, Experts Say - ABC News
49ers LB Chris Borland is retiring after one season rather than risk head injuries - The Washington Post
49ers' Chris Borland retires: NFL responds, cites safety progress - Los Angeles Times
Chris Borland to pay back part of signing bonus
49ers' Chris Borland, 24, retires because of brain injury concerns - Los Angeles Times
Chris Borland stuns 49ers with retirement announcement
Badgers who walked away from football after concussions
49ers' Chris Borland retiring at 24, wary of head trauma – The Denver Post