Chris Borland's retirement: Is an NFL player's brain really more
49ers' Chris Borland, 24, retires because of brain injury concerns
The NFL's Most Courageous Player, Who Retired After Just One Year
Is Chris Borland's retirement the beginning of the end for the NFL
Chris Borland and the Revenge of History
Why the NFL Should Be Scared of Chris Borland
Chris Borland, 24, Retires From NFL After Rookie Year
A Jolt to the System – Grow
Chris Borland stuns 49ers with retirement announcement
Former NFL player Chris Borland on Tackle Can Wait PSA