DENVER – The Colts were unable to take advantage of three takeaways and a six-point halftime advantage – which nearly became a 13-point lead in the third quarter – and saw their playoff odds take a major hit in a 31-13 Week 15 loss to the Denver Broncos on Sunday at Empower Field at Mile High.

The Colts are now 6-8. Their loss, coupled with the Houston Texans' win over the Miami Dolphins, clinched the AFC South for the Texans; the Colts are two games behind the 8-6 Los Angeles Chargers for the final spot in the AFC playoffs.

Denver scored 21 unanswered points in the fourth quarter to send the Colts back to Indianapolis with a loss.

Quarterback Anthony Richardson struck first with a 23-yard untouched dash to the end zone, capping a game-opening drive on which the Colts converted on third-and-11 (a 22-yard completion to wide receiver Josh Downs) and third-and-10 (a 15-yard run by running back Jonathan Taylor).

Linebacker Zaire Franklin jumped in front of a Bo Nix pass for an interception on Denver's ensuing drive, and the Colts turned that takeaway into a 37-yard Matt Gay field goal.

The Broncos took advantage of good field position to generate their first touchdown of the game, a 13-yard strike from Nix to tight end Adam Trautman.

Just before halftime, though, wide receiver Anthony Gould scampered 36 yards on a punt return, which set up a 49-yard field goal from Gay that put the Colts ahead 13-7 after two quarters.

Neither team sustained much offense in the first half – the Colts averaged 4.1 yards per play while the Broncos were at 3.3 yards per play.

Wide receiver Alec Pierce was evaluated for a concussion late in the first half and did not return to the game.

Cornerback Sam Womack III picked off Nix to begin the second half – on a third-and-1, Nix overthrew wide receiver Courtland Sutton – and the Colts nearly turned it into a momentum-shifting touchdown. However, officials ruled that Taylor did not possess the ball as he crossed the goal line on what would've been a 41-yard touchdown; Taylor dropped the ball, which rolled out of bounds for a touchback, ceding possession back to the Broncos.

After both teams traded punts, safety Nick Cross wiped out a Broncos drive when he intercepted Nix on a third-and-long from the Colts' 39-yard line midway through the third quarter. Broncos safety P.J. Locke, though, forced a fumble after wide receiver Michael Pittman Jr. caught a Richardson pass, with Denver recovering on the Colts' 31- yard line. Broncos kicker Wil Lutz turned Pittman's fumble into a 44-yard field goal, bringing the Broncos within three points with about five minutes left in the third quarter.

Broncos wide receiver Marvin Mims ripped off a 60-yard punt return early in the fourth quarter, which set up tight end Nate Adkins' 15-yard, go-ahead touchdown with just under 14 minutes left. The score gave Denver its first lead of the game; they wouldn't give it back, landing a haymaker on the Colts' ensuing possession.

With the ball in Broncos territory, the Colts called a double pass, with Richardson throwing to wide receiver Adonai Mitchell, who then threw back toward Richardson. Broncos defensive end Nik Bonitto read the play, though, and jumped in front of Mitchell's lateral, grabbing the ball and running 50 yards for a touchdown.

The touchdown put Denver up by 11 with 12:29 left in the game. The Broncos added another score on a Sutton touchdown late in the fourth quarter.

The Colts' defense held strong throughout the day, though – Denver only had one possession gain more than 40 yards, and their longest play of the game (until Sutton's 20-yard touchdown) was a 16-yard scramble by Nix.