The Lions said Stafford was forced to sit out "as a result of a false-positive test." The club added that the quarterback's next three tests were all negative and that Stafford "does not have COVID-19 and never has had COVID-19."
The 32-year-old, who was the NFL's first starting quarterback to hit the reserve/COVID-19 list, is coming off an injury-shortened 2019 campaign. In eight games, Stafford racked up 2,499 passing yards and 19 touchdowns against five interceptions.
Detroit also removed veteran cornerback Justin Coleman and leading wide receiver Kenny Golladay from the reserve group Tuesday and Wednesday, respectively. The team still has four players on the list, including former first-round tight end T.J. Hockenson.
The NFL's reserve/COVID-19 list is for players who either test positive for the coronavirus or are quarantining after close contact with an infected person.