KANSAS CITY, Mo. (AP) - Just a few weeks ago, the Kansas City Chiefs were unbeaten.
They were quickly becoming the NFL's ''it'' team, led by a seemingly impenetrable defense and a mistake-free offense.
That defense had slowly started to crumble. That offense is no longer playing so flawlessly.
The Chiefs are no longer undefeated, either.
Far from it.
Peyton Manning threw for 403 yards and five touchdowns on Sunday, four of them to Eric Decker, and the Denver Broncos rallied to beat the Chiefs 35-28 and seize control of the AFC West.
It was the third straight loss for the Chiefs (9-3), and the second to Denver (10-2) over that span.
That means the Broncos hold the tiebreaker in the division race, and Kansas City is virtually assured of playing a first-round playoff game on the road.
''You know, three in a row, any time you're doing that, you're not feeling good about that,'' Chiefs quarterback Alex Smith said. ''Losses are the nature of the game. You have to be able to overcome it. These last two we had a chance to win it, both times I felt like.''
The Chiefs certainly had a chance Sunday even after blowing a 21-7 lead.
Jamaal Charles scored from a yard out with 6:32 left to get Kansas City within a touchdown, and then the Chiefs forced a punt with 3:32 remaining to get the ball back.
Three long passes moved the Chiefs downfield, but Smith's pass to Dwayne Bowe in the end zone on fourth-and-4 with 1:45 left fell incomplete, allowing the Broncos to run out the clock.
''Hard-fought game,'' Chiefs coach Andy Reid said. ''Two good football teams playing each other, and it came right down to the end.''
Smith threw for 293 yards and two touchdowns for Kansas City, while Knile Davis returned a kickoff 108 yards for another score. Charles finished with 93 yards rushing.
Decker had eight catches for a career-high 174 yards for the Broncos, who have the AFC's best record. Montee Ball added 117 yards rushing.
''It was a great, gritty effort on the road,'' said interim coach Jack Del Rio, who led Denver to a 3-1 mark while John Fox was recovering from heart surgery. Fox is due back Monday.
''We figured they would have some type of surge early and I loved the way our guys responded,'' Del Rio said. ''It puts us in first place and now we'll go welcome Coach Fox back.''
Denver won despite missing a slew of injured players, including three starters on defense and tight end Julius Thomas, who has developed into one of Manning's favorite red-zone options.
No need to worry. Decker more than shouldered the burden.
Manning has 41 TD passes, breaking his franchise record of 37 set last season.
''Sometimes, when you play a team close to back-to-back, there are some ideas that are fresh in your mind,'' Manning said. ''We thought there were some chances to get down the field in that first game that we never got to. We wanted to get to some of those plays.''
The Chiefs, who lost for the third straight week, squandered far too many chances, including one right out of the gate when Smith was picked off by Wesley Woodyard in the end zone.
Still, Kansas City seemed to have more energy in the first half.
The Chiefs took the lead when Smith hit Junior Hemingway for a touchdown. And after Decker beat Brandon Flowers for a tying score, Davis took the ensuing kickoff 108 yards the other direction.
It was the longest return in franchise history, and the first TD return by a Chiefs player since Jamaal Charles took a kickoff back against the Steelers during the 2009 season.
Smith's touchdown pass to Anthony Fasano made it 21-7.
That's went Denver scored 28 unanswered points.
Manning hit Knowshon Moreno for a short TD just before halftime, and then hit Decker with two more touchdown passes in the third quarter. Decker's fade catch for a TD made it 35-21 early in the fourth, and that turned out to be all the points the Broncos needed.
''Any loss in this league hurts. This one was big for us and we came up short,'' Chiefs defensive back Quintin Demps said. ''It definitely stings.''
Notes: Chiefs TE Anthony Fasano (concussion) and LT Branden Albert (knee sprain) left the game and did not return. ... Charles became the first Chiefs RB with four 1,000-yard rushing season. ... It was Decker's sixth career 100-yard game. ... Denver has won 10 straight vs AFC West. ... Manning went over 4,000 yards passing for the 13th time. ... KC has allowed 1,118 yards and nine TDs passing during its three-game skid.
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