Armstead tested positive for COVID-19 and went on the reserve list Nov. 28.
He has started 10 games this season.
James Hurst started for Armstead the past two games.
Kelly went on the COVID-19 reserve list Nov. 29. He played the first five games, seeing action on 15 offensive snaps and 22 on special teams.
The Saints also designated defensive back Justin Hardee to return from injured reserve. He went on IR on Nov. 6 with a groin injury.
In addition, the Saints activated receiver Lil’Jordan Humphrey from the practice squad reserve list.