He played college football for the Stanford Cardinal and was selected by the San Francisco 49ers in the first round of the 2016 NFL draft.
[2] As a true freshman, Garnett appeared in 14 games for the Stanford Cardinal, playing both guard positions and fullback.
[3] Stanford eventually also started freshmen Kyle Murphy and Andrus Peat on the offensive line.
Garnett won the Outland Trophy and was named a unanimous All-American as a senior in 2015.
In practice on November 20, 2018, Garnett broke his thumb which sidelined him for the rest of the season.
[10][11] On February 3, 2020, Garnett signed a one-year contract with the Detroit Lions but was waived on August 9, 2020.