Mack has a long history with Kyle Shanahan. Originally drafted by the Browns 21st overall in the 2009 NFL Draft, Mack first linked up with Shanahan in Cleveland in 2014. The two were reunited in Atlanta during the Falcons 2016 Super Bowl run.
Getting back into Shanahan's offense was a major draw for the center when he was evaluating his options heading into free agency this offseason. "(I was) looking for a team that was competitive, and obviously there's a connection with Kyle Shanahan and the offense he runs," Mack said. "It's a system that I know I do well in – that outside zone scheme. It's just something that my body type – how I can move, the blocks I've done before – it's something I'm comfortable with. I know it. I'm good at it. I'm confident in it. And I know I can do it well."
Mack appeared in 46 games (39 starts) in five years at the University of California-Berkeley. At Cal, he became the third player in PAC-10 Conference history to receive the Morris Trophy, given to the best offensive lineman in the Pac-10 as voted by Pac-10 defensive linemen. As the 2007 and 2008 recipient, Mack became the first player to win the award twice since 1992.
In 2008, Mack became the first player from the University of California-Berkeley to win the William V. Campbell Trophy (previously the Draddy Trophy), college football's premiere scholar-athlete award. Mack earned a bachelor's degree in legal studies and continued on to earn a Master's in Education.
During his first 12 years in the league, Mack has made a name for himself as a top-ranked center. A six-time Pro Bowler (2011, 2014 & 2016-19) and three-time Associated Press Second-Team All-Pro (2013 & 2016-17), Mack was selected for the Pro Football Hall of Fame NFL All-Decade Team of the 2010's along with some familiar faces for 49ers Faithful, including Frank Gore, Joe Staley, Richard Sherman and Patrick Willis.
Mack has started all 179 games in which he appeared, completing a full 16-game season in 10 of his 12 years in the league. After suffering a concussion, the center's streak of 90 consecutive regular season starts ended in Week 16 of the 2020 season.
Mack was born in Los Angeles, Calif. He attended San Marcos High School in Santa Barbara, where he was named the Channel League's Co-Most Valuable Player on defense and earned a first-team all-league selection. He was also selected to the All-CIF team.