The postmortem on the Texans begins with the offense and quarterback Brock Osweiler, but to overlook the exceptional performance of the defense would be almost criminal.

The defense finished No. 1 for the first time in team history and was forced to carry the offense for most of a season that included a 9-7 record, a wild-card victory over Oakland and a divisional-round defeat at New England.

Of all the things the Texans need to accomplish in the offseason, re-signing defensive coordinator Romeo Crennel ranks among the most important - right behind hiring an offensive coordinator to replace George Godsey and drafting a quarterback.

Crennel, 69, said two weeks ago that he has no intention of retiring. When Bill O'Brien reached out to him to become his first defensive coordinator with the Texans in 2014, Crennel grabbed one of his four Super Bowl rings and headed for Houston.

O'Brien made it clear Monday how much he wants Crennel to return.

"I think Romeo has done a great job," O'Brien said. "I know we would love to have him back.

"I can tell you Romeo is a great coach and just means a lot to me personally. We would love to have Romeo back here."

Think about what the Texans achieved defensively this season.

Counting playoffs, they lost end J.J. Watt (15 games), cornerback Kevin Johnson (14) and outside linebacker John Simon (eight). Cornerbacks Johnathan Joseph and Kareem Jackson combined to miss five games. Inside linebacker Brian Cushing missed three.

Twenty defensive players started.

Crennel, the architect of the defense, made sure the losses didn't have a profound effect on the Texans' performance.

Nod to defensive staff

Crennel and his position coaches - Anthony Weaver (line), Mike Vrabel (linebackers) and John Butler (secondary) - did a tremendous job.

Three on defense - end Jadeveon Clowney, inside linebacker Benardrick McKinney and cornerback A.J. Bouye - developed into big-time players.

Bouye and Simon will be unrestricted free agents in March if the Texans are unable to re-sign them. If they do, imagine how good this defense can be with the return of Watt and Johnson, not to mention additions in the draft and free agency.

Think about how good McKinney can be in his third season. He was the only player in the NFL this season with at least 100 tackles and five sacks. He was voted second-team All-Pro by media covering the league.

"Just a great scheme," McKinney said about Crennel's 3-4 and multiple alignments. "The coaches did a great job of scheming, putting me in the right spots to make plays.

"The D-linemen did an unbelievable job keeping the offensive line off of me. I just ran around, played my game and had fun doing it."

Crennel's defense was a lot of fun to watch. Texans fans are excited about what's in store for next season.

O'Brien was asked about that Monday.

"I thought the defense played well this year," he said, "(but) next year is a totally different year. (A new) year is just nothing like the previous year, so I don't even begin to think about comparing this year to next year.

"(We're) looking forward to evaluating and trying to get better."

Well, we'll lay it out for O'Brien.

Room to improve

The Texans have a chance to be better next season. They need to get more sacks and more turnovers and score more than one touchdown on defense like this season.

One of the hallmarks of Crennel's defense was a ferociousness from kickoff to final gun. The defensive players never let up, and they were impressive to watch.

O'Brien was asked Monday what he was happiest with this season. His response was about the team, but it sounded perfectly suited to the defense.

"We play hard (and) we play very tough," he said. "I know some people would say that should be the case in the NFL, but I think when you line up against the Houston Texans, you know you're in for a 60-minute fight.

"That's probably the thing that makes me the most proud to be associated with these guys in that locker room."