The 25-year-old announced his retirement Friday at a Georgia TED event. He played for the Bulldogs from 2011-2015.
New England released the wideout prior to training camp in 2018. Mitchell missed the entire 2017 season and hasn't played since his rookie campaign, with his most recent knee procedure coming last summer.
The Patriots selected Mitchell in the fourth round of the 2016 NFL Draft. He had a strong rookie season during which he caught 32 passes for 401 yards and a touchdown, and helped the Patriots win Super Bowl LI.