Minnesota placed Thielen on the reserve/COVID-19 list Monday. He tested positive for the virus earlier this week but also had a negative test, according to NFL Network's Tom Pelissero.
Thielen, 30, is in the midst of another productive campaign, catching 49 passes for 646 receiving yards while adding a league-leading 11 touchdowns.
Rookie receiver Justin Jefferson will garner increased attention if Thielen is not activated for Sunday's game. Jefferson has been Kirk Cousins' favorite target in 2020, leading the Vikings with 848 receiving yards.
Minnesota is coming off a Week 11 loss to the Dallas Cowboys but has won three of its last four contests.