Gary Kubiak was fired by the Houston Texans just hours after they lost their 11th game in a row, and their second this season to the lowly Jacksonville Jaguars. And while Kubiak may have been the first coach to lose his job as a result of the 2013 season, he certainly won't be the last.

There are a handful of coaches who shouldn't feel comfortable at all about the state of their job at the moment, based on the way their teams are underperforming and failing to win games in the "what have you done for me lately?" NFL. And with only a month left in the season, these coaches have very little time left to prove they belong in their current positions.

So which sideline bosses are in the worst shape as we head into the final four weeks of the season? Let's look at numberFire's advanced data to see just how bad some of these teams really are, and see just how worried some of these coaches should be.

Mike Smith, Atlanta Falcons

Remember in the preseason when the debate was about whether or not the Saints with Sean Payton could catch up to the defending NFC South champion Falcons? Instead, the Falcons sit at the bottom of the NFC South with only three wins in 12 games, and Mike Smith's job has gone from secure to shaky in under a year.

So just how bad are things in Atlanta? On defense, I'm not sure things could get much worse.

The Falcons rank dead last in defense in the NFL using numberFire's in-house metric Net Expected Points, or NEP.

NEP is a measure of how many "expected points" a player - or team - gains or loses through his actions, or for a defense, the amount of expected points they allow or prevent based on their actions. You can read more about NEP by clicking here.

And not only are the Falcons last in this statistic for 2013, but they're in the neighborhood of being one of the worst defenses we've ever seen. They have posted a Total NEP on defense of 120.66, which means they've allowed offenses to gain 120 more expected points than the average defense would over the course of the season. If the season ended today, the Falcons would be among the 25 worst defenses dating back to 2000.

This is particularly embarrassing for Smith, who has a background as a defensive coach, including time as a defensive coordinator with the Jacksonville Jaguars.

So is that enough to cost Smith his job? The Falcons have become an offensive team under their defensive head coach, but he's managed to find success with similar rosters in recent years due to better fortunes when it comes to injuries.

With that in mind, Smith is safe for now, but will need to hope his offensive coaching staff stays in place next summer to help Matt Ryan and company maintain their top-flight offense status.

Greg Schiano, Tampa Bay Buccaneers

In only his second season in the NFL, Schiano has made waves in the national media for his methods more often than his actual coaching acumen. Rushing kneel downs and running quarterbacks out of town seems to be only part of the brash head coach's style, and it seemed to be wearing thin this season as the Buccaneers stumbled to an 0-8 start.

Tampa Bay reeled off three wins in a row to start to salvage Schiano's job, but have they done enough to rescue the former boss at Rutgers?

Schiano's Buccaneers have the 27th-ranked offense and 22nd-ranked defense according to Net Expected Points. Both of those numbers make sense for a bottom feeder in the NFC, and the poor defense is a negative for Schiano considering his defensive background as a coach.

His team's defense has improved in Adjusted NEP per Play since his debut in 2012, but his offense has taken a serious fall year over year. And considering that Mike Glennon was his choice at quarterback over Josh Freeman, he doesn't get many excuses for being at the bottom of the barrel on that side of the ball.

Over his first 28 games as a coach in the NFL, Greg Schiano has 10 wins, and most have come against losing teams. So maybe he's just not cut out for life in the NFL. Schiano is in trouble and has a lot to prove over the next four games for the Buccaneers.

Leslie Frazier, Minnesota Vikings

During his first three seasons as the defensive coordinator for the Vikings, Leslie Frazier helped head coach Brad Childress lead the team to two playoff berths with respectable defensive performances. But since taking over as head coach, things haven't been quite as successful.

Despite a playoff appearance in 2012 thanks to Adrian Peterson's incredible season, the Vikings have been trending downward since Frazier took over, especially on the defensive side of the football. This season, it's reached rock bottom for Minnesota under the former defensive coordinator turned head coach.

The Vikings have a Defensive NEP score that's less than half a point shy of the woeful total of the Falcons, placing Minnesota's 2013 defense among the worst since 2000. And again, considering Frazier is a defensive-minded coach, the performance of the defense is rather inexcusable.

There aren't a lot of good things to say about the Vikings, nor are there many good things to say about Frazier's future as the coach of the team. Frazier is in trouble and the team may move in an entirely new direction in coming seasons with a plethora of needs on offense and defense.

Mike Shanahan, Washington Redskins

Robert Griffin III isn't going anywhere, so if the Redskins are going to make any changes after their disappointing 2013 season, it will likely be at head coach.

Shanahan has a great history as a head coach, but most of his success pre-dates his time with the Redskins. In 2005, the Broncos finished with the fourth-best offense and sixth-best defense using numberFire's data.

With the roster he has in Washington, things aren't quite the same. This season, the Redskins have the 15th-ranked offense and a defense that ranks 28th, but is a distant 28th considering how bad the Falcons are.

The Redskins have invested a lot of draft stock into RGIII, and they need him to be the future of the franchise under center. If Shanahan can't make that work, he'll be out of a job in a hurry.

But he's an offensive-minded head coach with a bad defense and a recovering quarterback. Shanahan is safe for now, but he'll need to work with the front office to improve the defense to survive much longer.

Rex Ryan, New York Jets

Geno Smith is actively awful at quarterback for the New York Jets. The second-round pick from West Virginia that was thrust upon Ryan is the second-worst passer in the NFL on a per pass basis, ahead of only Josh Freeman, as he loses about a quarter of a point for the Jets with each throw.

So with that in mind, the defensive guru Ryan should be forgiven for having a bad offense. But considering the Jets' 32nd place ranking in NEP, a full 13 points behind the surging Jaguars and over 70 shy of the 30th-ranked team, maybe he shouldn't get a pass on that side of the football.

Nor should the former defensive coordinator of two of the best defenses of all time (the 2006 and 2008 Ravens) be excused from having the 15th-ranked defense in the league. There are excuses on defense as well, especially considering the loss of All-Pro cornerback Darrelle Revis before the season began, but the overall product for the Jets doesn't promote much faith in a coach who seemed to be out the door a year ago at this time.

Ryan has set a standard for himself that he's failed to reach over his last two seasons in charge in New York, and it will likely cost him his job in reality. But considering the terrible choice he has at quarterback and the talent lost on defense over the past two seasons, Ryan is safe in my book, but is quickly running out of time.