Gary Kubiak doesn’t want to use the word that has been circulated the most in describing his team’s performance Sunday at Kansas City

The Broncos weren’t flat, the coach said. Their 33-10 blowout loss to an AFC West rival on the road wasn’t for lack of effort, he added.

So what really happened Sunday, when the Broncos allowed 243 yards and three touchdowns in the first quarter alone, and saw their playoff hopes vanish?

“We just didn’t play well enough as a team to win,” Kubiak said simply. “That’s as poor as we’ve played defensively, and we’ve been pretty consistent defensively. Offensively, we’re not making the most out of possessions. We had two possessions in the second half with seven minutes remaining in the game. We turned the ball over on special teams. It was a group effort. It was not good enough as a group, coaches or players.” Related Articles September 23, 2020 Kiszla: The best Broncos can hope to get from this lost NFL season is Clemson quarterback Trevor Lawrence

September 23, 2020 Broncos Briefs: After fine, Vic Fangio vows to be more aware of wearing mask

September 23, 2020 Broncos, injuries and all, facing must-win scenario in Week 3 against Tom Brady and Tampa Bay

September 23, 2020 Panthers put Christian McCaffrey on injured reserve with ankle injury

September 23, 2020 Chargers’ team doctor punctured Tyrod Taylor’s lung, AP source says

But it hasn’t been for weeks. The Broncos (8-7) played their worst when they needed to play their best, but frustration had been building as problems two years in the making have gone unresolved: the lack of a running game, the porous offensive line and the absence of a true identity on offense.

First-year starting quarterback Trevor Siemian had his worst outing at Kansas City and “has to play a (heck) of a lot better than he did,” Kubiak said. But Siemian also averaged more than 300 yards passing in his previous six starts.

Injuries are partly to blame for Denver’s slide, as they landed fullback Andy Janovich (hand) and starting tailback C.J. Anderson (knee) on injured reserve, and have limited many key starters on both sides of the ball.

“I would just say what we became, from two backs to one back to some of the things that we did a little bit differently,” Kubiak said. “That’s not an excuse; I’m not telling you that. We became that last year and we found a way to survive and still be successful. That’s part of football. When you lose people, you have to adjust.”

And so before the Broncos boarded a plane home from Kansas City late Sunday, Kubiak told his players to try to clear their heads and begin to look ahead to next season. This season was lost. The finale against Oakland in Denver on New Year’s Day holds little value, save for possibly another audition for rookie quarterback Paxton Lynch and other young players, should Kubiak decide to rest some veterans.

“I’d like to sit here and say that we’ll play everybody,” Kubiak said. “I’ll make a decision on Paxton. We’ll see. We got home at 3:30 in the morning, so I haven’t made any decisions today. I’ll make those in the next couple of days.”

But the flight also afforded Kubiak time to reflect, as well. To look back on this season and last, and to think about the effort of his players and the work of his coaches. To compare all that went right en route to winning Super Bowl 50 and the many things that went wrong in the Broncos’ title defense.

“Last year, we played in a lot of really close football games,’ Kubiak said. “The thing we did last year, we were able to get leads in games. People had to play differently against us. They had to throw the ball. You go back to the playoffs, we scored first in all three of those playoff games, in the first possession.

“We haven’t gotten anybody in that position here in the last month. I think that’s been a big difference. Even though we’ve been in some close games, we haven’t been able to get somebody to play from behind and let our guys rush the passer, which is what we do best. It’s been tough.”

And it was never more magnified than Sunday. Against the Chiefs, the Broncos gave up 21 points on three scoring drives that each topped 75 yards.

This season the Broncos has scored a total of only 17 points on their first possessions, tied for third-fewest in the NFL. But they have allowed 55 points on opponents’ first possessions, tied for second-most in the league. Denver has dug itself holes too deep to climb out with its slow starts and a league-worst, first-quarter scoring differential of minus-61.

“We had ourselves in a pretty good position about four or five weeks ago,” Kubiak said. “We just haven’t played well enough, especially offensively, here down the stretch to continue to play some more. So it’s disappointing.”

But the problem is not new. And it’s not unlike the many others Kubiak and general manager John Elway will assess and try to correct in their extended offseason.

One decision Kubiak has already made? Looking ahead. Eyes are on 2017, not the end of 2016.

Broncos’ exit in numbers

A snapshot of Denver’s late-season slide and elimination from playoff contention:

5: Losses in the Broncos’ last seven games.

2: Touchdowns scored by the Broncos in their last three games.

26.8 percent: Third-down conversion rate (19-of-71) in their last five games.

367: Total yards rushing in those five games (3.46 average), compared with 791 yards rushing (4.35 average) by opponents in that span

Minus-32: Scoring differential in Weeks 12-16, since the Broncos’ bye. In their first 10 games, the Broncos had a scoring differential of plus-50.

.429: Winning percentage in close games (decided by eight or fewer points) this season, tied for 20th in the 32-team NFL. Last year the Broncos had a .750 winning percentage in close games, ranking No. 3 in the NFL.