As we get further into the season each game becomes bigger and bigger from the perspective of the playoff picture. The Kansas City Chiefs and Seattle Seahawks Week 11 game is no different despite being an AFC and NFC team playing.
Both teams are currently 6-3 on the season. From 1990 (when the current playoff format was adopted) to 2013, teams that start the season 6-3 make the playoffs 74 percent of the time, according to this handy chart from Five Thirty Eight (data via Pro Football Reference).
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A WIN by the Chiefs boosts them to 7-3 on the season. Teams that start 7-3 make the playoffs 84 percent of the time.
A LOSS by the Chiefs drops their record to 6-4 on the season. Teams that start the season 6-3 make the playoffs 62 percent of the time.
So regardless of what happens, the Chiefs are going to still be favored to make the playoffs based on what has happened in the past.
AP user RDOGuy has pointed out this weekly post from Five Thirty Eight which does a great job of explaining all the scenarios going on, and how each game affects everyone else in the AFC and NFC playoff picture.