Does Alex Mack's retirement set the 49ers back?
C Alex Mack Announces Retirement from the NFL
Pro Bowl center Alex Mack to retire from NFL after 13 seasons: report
Center Alex Mack Announces His Retirement After 13 NFL Seasons - Sports Illustrated Cal Bears News, Analysis and More
Pro Bowl center Alex Mack to retire from NFL after 13 seasons: report
49ers C Alex Mack retires after 1 year in San Francisco
Falcons' Legendary Center to Retire: Report
Could Colts Have a 'Return of the (Alex) Mack' Interest?
Former Falcons center Alex Mack announces retirement