With help from instant replay, the Broncos lead in the AFC West is now one game as the Kansas City Chiefs held off the visiting Broncos 31-to-27.
With a little more than two minutes left in the game, Denver's Mike Anderson plunged into the right side of the line on fourth down.
Officials on the field gave him a first down a couple of yards short of the 50. But Chiefs head coach Dick Vermeil threw the challenge flag and the officials overturned the spot.
The Chiefs then worked the clock before Denver got the ball back with three seconds left.
Jake Plummer -- who threw two costly interceptions -- had time for one heave and it fell incomplete.
Trent Green threw two touchdown passes and Larry Johnson rushed for 140 yards and two more scores for the Chiefs.
The Broncos are now 9-and-3 after having their four-game win streak snapped.