Armstead, 24, was twice placed on the reserve/COVID-19 list last season. He spent 19 days on the list the first time, then dealt with a groin injury and another illness before going back on the list. Players are placed on the reserve/COVID-19 list if they test positive for the virus or have been in close contact with someone who has.
Armstead was a fifth-round pick in 2019 and ran for 108 yards on 35 carries as a rookie. He was likely to have a larger role on offense last season with the team's decision to cut Leonard Fournette, but undrafted rookie James Robinson went on to win the starting job and ran for 1,070 yards and seven touchdowns, and catch 49 passes for 344 yards and three TDs.
The Jaguars drafted former Clemson running back Travis Etienne 25th overall last month.
Also on Monday, the Jaguars announced they've signed sixth-round draft pick Jalen Camp, a wide receiver from Georgia Tech.