The Seahawks do not have to beat the Vikings to keep their position for the 2019 playoffs. Minnesota is 8-3 and the other team somewhat entrenched in postseason seeding at this point. In a way, the Vikings need the game more than Seattle does because a loss means the Vikings have 4 losses on the year and drops them closer to the other teams fighting for a playoff berth.
Seattle is currently 3 games ahead of the Rams, plus they have a win over Los Angeles so they have a half-game advantage that way too. After the Rams, the Bears, Cowboys, Eagles (who Seattle has beaten) and the Panthers (who the Seahawks will play) all have 6 losses.