Chris Borland - Wikipedia
49ers' Chris Borland becomes latest young NFL star to retire early
Concussion Concern: LB Retires After One NFL Season
Chris Borland Retires: NFL Says Football 'Has Never Been Safer'
Chris Borland - San Francisco 49ers Linebacker - ESPN
[node:title] San Francisco 49ers Rookie Chris Borland Retires at 24
Chris Borland Retires at Age 24 Over Concussions
49ers' Chris Borland Retires from NFL at Age 24
49ers' Chris Borland retires over health concerns – The Mercury News