As the end of the NFL season approaches, teams are either preparing for the post-season or wondering where the year went wrong. For some teams, 2016 will be a year to build on and they can look ahead towards a future where they might contend for a championship.

For many others, though, that future looks dimmer and the window they might have had to win a Super Bowl could be closing.

Here are several teams whose windows are starting to inch down, if they already haven’t slammed shut.

Denver Broncos

The Broncos are in an odd spot.

On the one hand, they continue to have a dominant defense and have multiple skill position players on offense who other teams would kill to have.

On the other hand, they have no quarterback right now (the jury is still out on both Trevor Siemian and Paxton Lynch), the offensive line is a mess and the backfield is one big question mark. There’s a fair chance they could miss the opportunity to make another run with the defense at optimal  peak performance.

It’s especially tough given the increased competitiveness of the AFC West. The Oakland Raiders and Kansas City Chiefs feel like teams on the rise, which will make it tough for Denver to make in into the post-season. We saw this year how thin the margin for error was to make the playoffs.

Denver has to figure out how to finish building the offense while also keeping the defense on top.

It’s unlikely that the window will slam shut immediately, but there’s a feeling when looking at this team that it might be starting to slide down in the next few years.

Arizona Cardinals

Last year suddenly feels like an aberration—or maybe the loss in the NFC Championship game was more a revelation of what this team is than we thought.

The offensive line is no good, the wide receivers fell apart, Carson Palmer is ancient and the defense is inconsistent.  Worse, when Palmer is done—which could be this offseason—there’s nobody behind him that the team can rely on.

It’s hard to get a read on what this team is. Statistically, the defense looks good but when you dig into the numbers the last month or so, it collapsed. It’s one thing to lose when the offense lets you down repeatedly, but it’s another when the defense is also getting blown off the field as happened against New Orleans, Atlanta and Seattle.

The bright spot here is running back David Johnson, but he’s not carrying them to a championship. A running back can’t do that on his own—just ask Barry Sanders.

It feels like this team is done contending unless they come up with a real answer at quarterback.

Baltimore Ravens

While the Ravens recovered from a four game skid when they returned from the bye week, looking at the team it’s hard to imagine this team is facing anything but a closing window.

While Joe Flacco continues to play good football, the receivers are questionable, the run game is shaky and the rest of the offense isn’t exciting. The defense came to the rescue for part of the season, but it’s been an up and down affair.

They seemed to beat up on weaker teams this season (Cleveland, Cincinnati) while often struggling against the cream of the crop. While they did beat Pittsburgh once, they lost when it counted in Week 16, and got soundly beat by New England and Dallas.

What could keep them in the hunt is a relatively weak AFC and their defense.

What looks like it will knock them out is most of the rest of the team.

New Orleans Saints

The Saints continue to go as far as Drew Brees’ arm will take them, but that counts for less and less these days.  Brees may lead the NFL in passing yards, rank second in touchdowns and lead in yards per game, that didn’t translate to enough wins.

For wins, the Saints need a defense and we’ve hit the point where it’s hard to imagine them figuring out what that will take. You can fire all the Rob Ryan’s in the world, but if you’re still ranking 25^th in the NFL defensively, maybe your defensive coordinator isn’t the problem.

Atlanta is always a solid team and Tampa Bay is on the rise. If Carolina rebounds from this year’s sorry effort—and they have the youth and ability to do it—the Saints are going to have a tough time in their own division, forget factoring in having to beat teams like Green Bay, Seattle and Dallas.

And what happens when Brees retires or his play degrades?

For the Saints, the window feels like it has pretty much shut. When Brees goes, it will completely slam closed.

It might even break.