Throughout the existence of the franchise, the Houston Texans have been more known for a sound defense than a overpowered offense. Even when Matt Schaub was at his peak, the defense carried the team to the playoffs. This season, however, was a totally different story.

Under rookie quarterback Deshaun Watson, the Texans' offense averaged 34.7 points per game, including 57 against the Tennessee Titans, a playoff team. However, the team only went 3-3 in that span. Why? Because of the team's lackluster defense. And it wasn't any better the rest of the year.

Yards-wise, it wasn't so bad; they were right in the middle of the pack in yards allowed per game. The real issue was points allowed as they were the worst in the league at 27.3 per game. Thirty of the forty-four touchdowns given up were through the air. They've also had a top 10 DVOA in four of the past five seasons. However, their DVOA this year was a paltry 23rd. 

Some would attribute these poor performances to the J.J. Watt and Whitney Mercilus injuries. However, the pass rush was similar to last season's. In fact, the team had more sacks this year (32) than last year (31). Their absences didn't help whatsoever, but it's definitely not an excuse for the defense's subpar play. 

One reason is A.J. Bouye's departure from the team. The undrafted cornerback from the University of Central Florida climbed his way up the depth chart back when he was with the Texans until he became the best member in the secondary. However, he left the team last offseason to the divisional rivals Jacksonville Jaguars for a five-year $67.5 million contract. Now, he is a part of the best cornerback do in the league with Jalen Ramsey.

Hindsight is 20 20, but letting AJ Bouye leave was a horrible mistake. Now, the Houston Texans must face both him and Jalen Ramsey at least twice a year. Photo Credit: Logan Bowles/Getty Images.

Now, the Texans have to rely on Kareem JacksonKevin Johnson, and an old Johnathan Joseph for pass coverage. Spoiler: it didn't work well. However, even then, one player can't lead to a night and day change. The other difference between this and last year? Mike Vrabel.

Mike Vrabel's lone year leaves much to be desired

Even with Crennel's success helming the defense, the Texans promoted Vrabel to defensive coordinator because they were scared that another team would pry him away. They had reason to fear, the San Francisco 49ers had shows a lot of interest the season before. In order to keep Crennel, they made him the assistant head coach.

From the get go, the former Patriot linebacker struggled as a defensive coordinator. He made plenty of bad calls in the opening game against the Jaguars. This didn't change throughout the season, as the team gave up big play after big play. This was very apparent in the games against the New England Patriots and Seattle Seahawks. Many blame head coach Bill O'Brien with him late game decisions, but the reality is that the defense shouldn't have let their opponents be within striking distance.

Often, when a receiver is left wide open down the field, it is because of a bad play call. There were way too many occasions where that occurred this season and that rests on Vrabel's shoulders. He may get better with more experience calling plays, but 2017 suggested that he's a far better positional coach than coordinator. 

Romeo Crennel hopefully will bring back old defense

After defensive coordinator Wade Philips was fired in 2014, Crennel was brought in, his first job since coaching the Kansas City Chiefs in 2012. He was one of the highest paid defensive coordinators while with the Texans, and rightfully so. The defense was great under his command, even without Watt during the 2016 season.

Romeo Crennel was a great defensive coordinator for the Houston Texans and will look to continue his success leading that unit after Mike Vrabel's departure. Photo Credit: Wesley Hitt/Getty Images.

The players did like Vrabel a lot, but Crennel has experience and will get the job done. Even if the Texans are unable to improve the secondary in free agency or during the draft, Crennel would be able to make them adequate. If Watt and Mercilus can stay healthy, he won't need an outstanding secondary, opposing quarterbacks won't have enough time to find open receivers because the pass rush will be barreling towards them. 

Still, if the Texans want their old defense back, they have to make some changes. Joseph is on the last year of his contract and shouldn't come back unless he takes a massive pay cut. 2018 may also be Jonson's last season to prove that he can be a good player in the NFL. Jackson is a great tackler, but is horrible in coverage. He may be a solid safety, but it's also a huge risk putting him there. And it's not like there aren't players that the Texans can target in free agency to help Crennel. 

How will Vrabel do with the Tennessee Titans

Don't worry Titans fans, I've got a passage for you. It's risky to trust an inexperienced coach with an improving team. Apparently after Mike Mularkey's firing, Vrabel was the top candidate for the job. The reason for the firing was not because of the postseason, where the Titans upset the Chiefs, but a lackluster regular season, where the team went 9-7 and barely sneaked into the playoffs.

The Titans' defense was average this past season and could improve under Vrabel. If he performs as expected by the owner and fans, then the Titans can prove to be a dangerous team. However, that's a huge if. If he continues to perform like this past season, then this would be a borderline disastrous hiring, sacrificing a few years of this young team's improvement for the prospect of getting an exciting head coach.

The other issue is that nobody knows how he will do on the offensive end. They did solid utilizing both Derrick Henry and Demarco Murray in the running game this past season. However, with Murray's age, the Titans will probably opt to use Henry more often.

What Vrabel must focus most on, however, is getting Marcus Mariota out of his slump. In 2016, the Oregon QB looked like the Titans' quarterback of the future, mixing his passing and running abilities to great success. However he fell back in 2017, making a lot of mistakes and not scoring enough. This led to his worse season QBR by far in his young career.

Mariota is the centerpiece of the Titans' offense and looked to be a great quarterback before he fell off this season. Vrabel must find de wae (typo intended) to get him back on track. Photo Credit: James Kenney/AP Photo.

Since the Titans also need a new offensive coordinator, Vrabel and the rest of management must find someone that can work with Mariota. So far, the team is interested in Ohio State's offensive coordinator Ryan Day, who also happens to be Mariota's former QB coach in Oregon. This would be a great hire, and would help Vrabel focus on the defense he was hired to improve. 

Now you're probably wondering why he was such a commodity despite his lackluster year with the Texans. The Bill Belichick connection helps a lot. He is also extremely respected by other players and his peers. He's got the it factor and has the potential to lead a team far. If he is able to utilize what he learned under Belichick well, he can become a great head coach.

Overall, the Vrabel hiring is extremely risky given his lack of experience. But if the Titans can get Day and Vrabel improves at play calling, this franchise could prove to be very dangerous.