49ers' Patrick Willis retires after injury-shortened season
49ers' Patrick Willis retires after injury-shortened season – The Mercury
San Francisco 49ers LB Patrick Willis expected to retire
Patrick Willis Explains Decision to Retire from NFL
Chris Borland's early retirement shifts focus of head injuries in NFL - Los Angeles Times
Patrick Willis retiring from 49ers after injury-shortened season, NFL
Patrick Willis of San Francisco 49ers retires - ESPN
Report: 49ers expect Patrick Willis to retire
San Francisco 49ers: Justin Smith Versus Patrick Willis in the Hall of Fame, News, Scores, Highlights, Stats, and Rumors
Patrick Willis retiring from 49ers after injury-shortened season, NFL
Has there been another NFL player that was very talented that retired at an earlier age than Andrew Luck? - Quora