Too many failures in the red zone combined with an untimely turnover in the fourth quarter doomed the Broncos to a 30-23 loss against the Buffalo Bills on Sunday at Invesco Field at Mile High.

The Broncos sprinted to a 13-0 lead but settled for too many field-goal attempts without getting touchdowns. After having a chance to clinch the AFC West crown each of the past two weeks, the Broncos must earn a victory in a winner-take-all showdown Sunday night at San Diego.

FIRST QUARTER: Broncos 10, Bills 0

The Broncos start the game by moving the ball at will and, after missing seven games because of a groin injury, cornerback Champ Bailey makes an immediate impact upon his return.

The Broncos take the opening kickoff and march 80 yards in eight plays, with P.J. Pope carrying the ball five times for 42 yards before quarterback Jay Cutler starts the scoring with a 2-yard run on a bootleg.

Bailey drops Bills running back Marshawn Lynch for a 1-yard gain on Buffalo's first play and sacks quarterback Trent Edwards on the second play, helping to force a punt.

The Broncos march down the field again, getting a 71-yard run from receiver Eddie Royal on a reverse before the drive stalls inside the 10-yard line.

The Broncos settle for a 23-yard field goal by Matt Prater to extend the lead to 10-0.

Buffalo still is unable to move the ball, punting after a false start and an intentional-grounding penalty caused by pressure from linebacker D.J. Williams. The Broncos move into Bills territory again as the quarter ends on two passes from Cutler to Brandon Marshall covering 27 yards and another 11-yard pass to Royal.

SECOND QUARTER: Broncos 13, Bills 10

The Broncos get another field goal from Prater, this one from 30 yards, to extend the lead to 13-0.

Buffalo's offense finally gains some momentum, picking up its first few first downs and moving into Broncos territory.

A 14-yard pass to Roscoe Parrish becomes more damaging with a roughing-the-passer penalty against Broncos defensive end Elvis Dumervil, setting up a 37-yard field goal by Rian Lindell that trims the Broncos' lead to 13-3.

The Broncos begin to put another steady drive together, getting a 12-yard pass to Royal and a 12-yard run from Tatum Bell, who assumes the bulk of the running back chores with Pope on the sideline because of a hamstring injury.

But two penalties - a holding call against center Casey Wiegmann and a delay of game - force a 54-yard field-goal attempt by Prater that falls short.

Buffalo firmly takes over the momentum going into the break, driving down the field and getting a 2-yard touchdown run from Lynch with 15 seconds remaining in the half to pull to 13-10.

THIRD QUARTER: Broncos 20, Bills 16

Buffalo continues to build on the momentum it gained at the end of the first half, taking advantage of a short kickoff by the Broncos to tie the score 13-13 on a 49-yard field goal by Lindell.

The Broncos offense, after moving the ball with ease through much of the first half, begins to contribute to the team's unraveling.

After their first two plays go nowhere, Marshall appears to bail out the offense with a 24-yard catch, but he is sandwiched near midfield and the Bills' Reggie Corner recovers the fumble.

Buffalo takes advantage of the game's first turnover and, aided by a pass-interference penalty against Dre Bly and an 11-yard run by Edwards, the Bills take their first lead at 16-13 on a 28-yard field goal by Lindell.

Just when it seems the Broncos are going to completely implode, veteran tight end Daniel Graham comes to the rescue. The Colorado native makes two catches for 47 yards on the Broncos' next drive, including a key 23-yard reception on third down. After another third-down completion to Brandon Stokley, the Broncos retake the lead on a 6-yard run by Cutler with 38 seconds remaining in the quarter.

FOURTH QUARTER: Bills 30, Broncos 23

The Broncos' momentum is short-lived as a 65-yard pass to Fred Jackson sets up a 3-yard touchdown pass from Edwards to Steve Johnson that gives the Bills a 23-20 lead.

Cutler, though, helps the Broncos answer, hitting tight end Tony Scheffler for 36 yards and finding Royal for an 11-yard gain that helps set up a 43-yard field goal by Prater that ties the score 23-23.

Buffalo answers immediately against the Broncos' reeling defense, taking advantage of another short kickoff to regain the lead on an 8-yard touchdown run by Jackson.

A defensive-holding penalty gives the Broncos new life and nullifies a Cutler interception, and he promptly hits Marshall with three passes for 38 yards to move into scoring position. Cutler does not get a similar reprieve later in the drive, when linebacker Kawika Mitchell intercepts Cutler at the 2-yard line.

The Denver defense holds, forcing a punt after three runs by Buffalo, and the Broncos get one last shot. A 13-yard pass to Stokley on third down and a 12-yard pass to Marshall move the Broncos into scoring position, but their hopes at clinching the division end when the ball is knocked from Stokley's hands on a fourth-down throw into the end zone.