The Chiefs (14-2) have only lost one truly competitive game this season — a Week 5 stinker against the Raiders — and have established a reputation for letting games get interesting before cranking up dramatic or spectacular finishes to win. Their only other loss was to the Chargers in the last week of the regular season, with quarterback Patrick Mahomes and other starters on the bench. Kansas City enjoyed a bye week during the wild-card round as the A.F.C.’s top seed, giving Mahomes an extended layoff to prepare for a deep playoff run.
But the Browns (11-5) are thriving in their underdog role in the playoffs, as evidenced by the glee with which they dispatched the Steelers.