Thompson was placed on the reserve/COVID-19 list after testing positive for the virus, Michael Gehlken of The Dallas Morning News reports.
Thompson won't play in Sunday's game against the Giants. The Cowboys will miss the playoffs with a loss or a Washington win. Depending on when Thompson tested positive, he may not be cleared in time for the first round of the playoffs. If Xavier Woods (ribs) is also unable to play, Reggie Robinson likely will start at safety in Week 17.