Garrett was interested in joining the NFL, but despite having what he called "a great Pro Day" and having some workouts with the Detroit Lions and the Los Angeles Rams, he was not picked up.

After that, he signed with an agent and continued to get minor roles in TV shows like Hawthorne, CSI: Miami, and NCIS, as well as films like Transformers: Dark of the Moon.

In 2016, Garrett landed two key roles; the first one, as Lieutenant TAO Cameron Burk on TNT's The Last Ship, and the second as Secret Service agent Mike Ritter on ABC's Designated Survivor.

David Guggenheim, creator and executive producer of the latter, said they "needed someone who could throw President Tom Kirkman into a car", but that had "an emotional core goodness".

[4][5] In late 2018, he was cast as Mar Novu / The Monitor in the Arrowverse crossover event "Elseworlds" on The CW, which connects storylines from The Flash, Arrow, and Supergirl.

He was later upgraded to a series regular for those shows, as well as Batwoman, to ensure his availability for all appearances prior to and in the "Crisis on Infinite Earths" crossover.