Borland retires at 24, citing health concerns
NFL faces no danger from new trend of early retirees
Chris Borland talks 'early' retirement in UW-Madison guest lecture
Chris Borland and the Revenge of History
49ers' Chris Borland, 24, retires because of brain injury concerns - Los Angeles Times
Chris Borland, 24, to retire from NFL, cites fear of concussions
49ers' Chris Borland Retires from NFL at Age 24
Former Badger returns home with a mission
San Francisco 49ers Chris Borland Retiring at 24, News
NFL standout quits, citing brain damage risk - WHYY
Chris Borland's retirement won't slow the NFL pipeline – but science could, NFL
NFL players giving up millions and retiring out of nowhere before age 30 is becoming a trend