49ers' Borland retires after rookie year over head trauma fears
Patrick Willis injury: San Francisco 49ers' linebacker will have
49ers LB Patrick Willis retiring after injury-shortened season
San Francisco linebacker Patrick Willis announces his retirement
49ers LB Patrick Willis retiring after injury-shortened season
49ers linebacker Patrick Willis retiring after injury-shortened season
Patrick Willis Explains Decision to Retire from NFL
Patrick Willis' Shock Retirement Marks Official End of Jim
Early retirement: Willis called it quits in his prime
49ers LB Patrick Willis retiring after injury-shortened season
Patrick Willis retiring after eight seasons with 49ers
Ex-49ers star Patrick Willis reflects on making team's hall of fame
49ers Patrick Willis Officially Announcing Retirement - CBS Sacramento
49ers LB Patrick Willis retiring after injury-shortened season
49ers' Chris Borland, 24, quits NFL over concussion worries