Patrick Willis retiring after eight seasons with 49ers
Patrick Willis Explains Decision to Retire from NFL
49ers Linebacker Quits After 1 Season, Citing Safety Concerns : The Two-Way : NPR
49ers' Patrick Willis retires 'happy' – The Mercury News
Patrick Willis Explains Decision to Retire from NFL
Detroit Lions' Calvin Johnson is retiring and is 'at peace with it'
49ers' Patrick Willis retires 'happy' – The Mercury News
Might ex-49ers star Patrick Willis come out of retirement?
49ers' Patrick Willis reportedly set to retire at age 30 - The Washington Post