The Vikings placed Cook on the reserve/COVID-19 list Thursday.
Though Minnesota hasn't revealed whether Cook tested positive for the virus, Andrew Krammer of the Minneapolis Star Tribune notes that the running back has been following the NFL's protocols for unvaccinated players this season. With that in mind, he'll have to complete a five-day quarantine if he was deemed a close contact of an infected person, or a 10-day quarantine if he tested positive for the virus. That means that Cook won't be available to play for at least Sunday's game against the Rams, and he could also be at risk of missing a Week 17 matchup with Green Bay on Jan. 2 if he tested positive. Minnesota returned Alexander Mattison from the reserve/COVID-list Wednesday after he previously sat out the Vikings' Week 15 win over the Bears, so he'll likely be in line for a turn as Minnesota's lead back against the Rams.