Garnett, 26, is a former first-round pick by the 49ers in the 2016 NFL Draft. He was entering the second year of a four year $9.304 million rookie contract when the 49ers waived him coming out of the preseason.
Garnett worked his way back from an offseason knee scope last year and tried out for the Bears, Raiders, Broncos, Texans, Titans, and Packers but never signed a contract.
The Lions signed Garnett to a futures deal back in February but wound up cutting him back in August. Washington signed him to their practice squad last month and was promoted for Week 3 before reverting back to the taxi squad.
In 2018, Garnett appeared in seven games for the 49ers.