INDIANAPOLIS — The Broncos combusted.

Then they were busted.

The roof at Lucas Oil Stadium didn’t fall on the Broncos. They fell on their own volition, and they didn’t raise high the roofbeams.

In an open-and-shut case, the retractable ceiling was not closed for the Sunday afternoon-evening game, despite temperatures that dipped into the mid-40s by the second half. Indianapolis Colts owner Jim Irsay, who makes the final decision on the roof, obviously was playing gamesmanship with his former quarterback. Irsay apparently believed the chill could affect Peyton Manning negatively.

The Broncos were cold enough on offense and defense without provocation.

They fell behind 17-0. And, even though the Broncos tied the Colts at 17 and 24, they would fail to tie again, or win — first on a Manning interception with 6:06 remaining and, finally, in an effort(less) attempt to get another chance.

Shoddy defense interspersed four penalties — two on Aqib Talib — allowing Indy to keep possession for the final six minutes and 16 plays.

And Andrew Luck, the successor, beat the predecessor for the third time in four matches with a clock-consuming kneel at the Broncos’ 1-yard line.

Manning — in, likely, his last game ever “Back Home In Indiana” — shrugged afterward.

“We obviously didn’t play well enough,” he said and walked from the locker room with head bowed. He stopped en route to the bus for a meet-and- greet with a U.S. Marine corps color guard. But his wish to set the NFL passing record fell short by 3 yards, and the NFL victory total remains shy by one. Those marks will have to wait until Sunday at home against Kansas City. But the undefeated streak falls, and the Broncos fall behind New England and Cincinnati in the game of AFC thrones.

When I asked Broncos coach Gary Kubiak if the Broncos lost their cool as they lost the game, he suggested the Broncos made a gallant gallop to come back but mistakes caused them to come undone. And as he does, Kubiak put the blame on himself. “Did we lose our cool?’ I thought we kept our composure in the second half . Did we do some not very smart things at the end? I agree with that. We just weren’t able to close the deal after battling our way back.”

Three Pro Bowlers in the Broncos’ secondary accepted the responsibility.

“We played awful,” cornerback Chris Harris said.

“We put ourselves in a hole, and we couldn’t dig out,” safety T.J. Ward said.

“We didn’t play well defensively, and we gave them too much. It was our fault,” cornerback Talib said.

Harris left the game at one point because of NFL concussion protocol, but returned. He wanted to cover Colts’ receiver T.Y. Hilton, but Hilton, questionable with a leg injury, caught like Ritz, and Luck threw like Carlton.

Ward, who had to sit briefly with a leg issue, drew a critical defensive holding flag on the Colts’ final possession.

And Talib was found guilty of unnecessary roughness during a dead ball when the Colts were in position to get a field goal with 2:35 to go. The personal foul, poking tight end Dwayne Allen in the face, gave Indianapolis a first down.

Talib was removed by the coaching staff to the sideline, then went back on the field after a timeout and drew another unsportsmanlike penalty and was ejected.

In the meantime, linebacker Danny Trevathan, who was credited with 19 tackles (seven solo), was called for defensive holding on a fourth-down field goal attempt, and the Colts got a first down and the victory.

Kubiak would not single out anyone on either side of the ball for the loss — Manning for the interception, the defense for not stopping the Colts or committing foolish penalties.

However, as impressive as the team triumph over Green Bay was a week ago, this defeat was just as unimpressive.

If the Colts hadn’t pulled off a stupid human trick and punted to Omar Bolden on the last play of the first half, they could have won in a walk. Instead, after Bolden’s touchdown sprint, the score was 17-7.

The Colts aren’t good. And the Packers don’t feel so fine, either, after a loss at Carolina.

“We’re all right,” Ward said. “We’ll get back to work on Monday, and start another streak.”

But, on Sunday, the Broncos were not all right, and they flamed out.

Woody Paige: woody@woodypaige.com or @woodypaige