Now we know that decision has been made.
Per Mike Silver of Bally Sports, Mack will retire after 13 seasons in the league.
Mack began his career with the Browns as the 21st overall pick of the 2009 draft. He played seven seasons for Cleveland, starting 101 contests.
Mack played under now-49ers head coach Kyle Shanahan with the Browns in 2014 and reunited with him with the Falcons in 2016. Mack started 78 games in five seasons for Atlanta before signing with the 49ers to once again reunite with Shanahan last year.
Mack ends his carer as a seven-time Pro Bowler and three-time second-team All-Pro. He started all 17 games and made the Pro Bowl for San Francisco last year.
The 49ers now have a vacancy at center. JC Tretter is the top available free agent at the position, as he was released by the Browns in March. Jake Brendel, Daniel Brunskill, and Keaton Sutherland are regarded as internal candidates for the role.