Stafford is the latest star on the Lions' offense to hit the new reserve list as team's leading wide receiver Kenny Golladay and 2019 first-round tight end T.J. Hockenson also hit the reserve group earlier this week.
Stafford, 32, was on track for one of the best campaigns of his career over the first eight games of the 2019 season before suffering a back injury that sidelined him for the rest of the year. He completed 64.3% of his pass attempts for 2,499 yards and 19 touchdowns against five interceptions in eight games.
The new reserve list is for any player who either tests positive for COVID-19 or who is quarantining after coming in close contact with an infected person.
Players who had contact with an infected person may return to camp after having two negative tests for coronavirus within 24 hours. Those players will also be tested daily in the first week after returning.