The Texans have reached an awkward crossroads upon the close of their dreadful, injury-plagued season as they approach a critical decision that will have major implications for the future of their franchise.

When the Texans return to Houston on Sunday night following their meaningless season finale against Indianapolis, owner Bob McNair is faced with a difficult, complicated choice: Does he go forward with coach Bill O'Brien or general manager Rick Smith?

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While the four-year partnership between O'Brien and Smith has produced two AFC South division titles, the relationship between the two is characterized as problematic and could lead to an either-or-situation going forward, according to multiple sources with knowledge of the situation but not authorized to speak publicly.

"It's toxic," one source said. "It's dysfunctional."

Another source speculated that Smith and O'Brien could keep working together but that it would be an "uneasy alliance" that's somewhat untenable.

A third source with knowledge of the situation said he would be "kind of surprised" if the Texans don't make a change.

While O'Brien has always described his relationship with Smith as good, this has been a time of serious uncertainty with a fair amount of anxiety at Kirby Drive as McNair, who likes continuity, contemplates how he'll proceed. Should McNair decide to punt and put off the decision until O'Brien's contract expires next year, sources say the Texans could be maintaining a difficult work environment.

O'Brien is entering the final year of his contract in 2018. If O'Brien becomes available through a firing - O'Brien has stated he won't quit - or via a trade, which would be a complicated scenario that would involve a hefty amount of draft-pick compensation, he would arguably become the top free agent coach on the marketplace with several franchises interested in acquiring the former New England Patriots offensive coordinator and Penn State coach.

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Among the many potential destinations for O'Brien, if he becomes available, and jobs become open: Detroit with general manager Bob Quinn, who worked in New England, Arizona with general manager Steve Keim and Tennessee with general manager Jon Robinson, who also has a New England background.

It would be an ideal time for O'Brien to become a free agent because industry sources predict so many head-coaching positions will be available in this hiring cycle.

"I think Bill is an excellent football coach," said former Texans and Washington general manager Charley Casserly, an NFL Network analyst. "I think if he were a free agent, he would have a job before he left the building and got home."

O'Brien won two division championships with stopgap quarterbacks and is 31-32 overall, including a 4-11 mark this year during a season in which the Texans have lost standouts like quarterback Deshaun Watson, defensive end J.J. Watt and outside linebacker Whitney Mercilus to season-ending injuries. Star players, including Watson, wide receiver DeAndre Hopkins and outside linebacker Jadeveon Clowney, have enthusiastically endorsed O'Brien and say they want the hard-nosed coach back for 2018.

The Texans have endured a rough year, including experiencing Hurricane Harvey.

"OB can flat-out coach," said an NFL executive, who asked not to be identified when speaking about another team's coach. "I would have him on a very short list of guys I would want to talk with right away if we were in the market for a coach. When Watson was healthy, they had it rolling. When he got hurt, they just weren't the same team.

"What he did with Watson this year and previously with Tom Brady is impressive and I've heard good things about him as a leader. It will be interesting to see what happens with them."

O'Brien said this week that he would be willing to coach the Texans next season, even without a contract extension. That would an unusual, but not unprecedented situation.

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"Yeah, sure," O'Brien said. "As long as they want me to coach this team, I'll coach the team. We have a good staff, we work very hard. It hasn't been a good year, we know that. We know the business. We're not blind to what goes on in the NFL.

"Everybody understands that it's a bottom-line business but we believe in what we do and again, a lot of those decisions aren't made by me. So, I just do the best job I can to work with the staff and the players to try to get a win on Sunday."

The Texans were decimated by injuries this season having 18 players placed on injured reserve, robbing them of their depth and exposing holes on the roster. The offense collapsed without Watson and the defense ranks last in the NFL with the most points allowed in the league, surrendering 27.6 points per game.

Smith engineered the trade to draft Watson, a multidimensional former Clemson All-American who dazzled as a rookie before tearing his anterior cruciate ligament. Smith is under contract through 2020 after signing a contract extension last year.

Smith has a strong track record of drafting in the first round, including selecting Watt, a three-time NFL Defensive Player of the Year, Hopkins, Clowney and second-round linebacker Benardrick McKinney and center Nick Martin.

However, there have been several misses. That includes second-round picks offensive guard Xavier Su'a-Filo and safety D.J. Swearinger and third-round wide receivers Braxton Miller and DeVier Posey, offensive tackle Brennan Williams and nose tackle Louis Nix. The talent in the offensive line — after trading Pro Bowl left tackle Duane Brown following a contract holdout and Brown's blasting McNair for his "inmates running the prison" comment — and secondary have declined to the point they've become substandard.

The Texans lost cornerback A.J. Bouye during free agency to the Jacksonville Jaguars in March when he signed a five-year, $67.5 million contract as they were outbid, but could have retained him by making him their franchise player. Bouye was named to the Pro Bowl this season as the Texans dipped from second in pass defense last year to 26th this season.

Smith has an extremely close relationship with McNair and his son, Texans vice chairman and chief operating officer Cal McNair. A member of the NFL competition committee, Smith is in his 12th season as general manager and seventh as executive vice president of football operations.

Smith last spoke with reporters when the Texans arrived at The Greenbrier in West Virginia for training camp. Smith has not responded to a request for comment this article.

Ultimately, the relationship between Smith and O'Brien is pivotal to the future of the Texans.

"It's crucial because you really have to be in unison and on the same page," said Casserly while speaking generally about coaches and general managers. "They have to be able to work together. They don't have to like each other."

If O'Brien returns, he would be coaching an offense headlined by one of the NFL's most dynamic young players in Watson, a true dual-threat quarterback. The offensive line, though, could need as many as four new starters. The secondary needs to be retooled. The pass rush should get a huge boost with the healthy return of Watt and Mercilus.

"The big positive is the quarterback is really excellent," Casserly said. "The offensive line definitely needs work. If they can somehow get the tackle position corrected that would really help everything. Watson saved their season with how he was able to scramble around and mask the deficiencies.

"They need help in the secondary. The pass rush was probably masking some things back there. This is a team that could turn their record around fast. It's not a huge rebuilding project. They have a lot of talent. They have two excellent building blocks on offense and defense in Hopkins and Clowney."

Inside the Texans' locker room, O'Brien has strong support from his players. They've bought into his style and he's made strides in the past few years to build his relationships with players.

"He's very competitive, he loves football," Texans veteran linebacker Brian Cushing said. "I think he treats the guys fairly. He's a player's coach, so there's a bunch of things that obviously we enjoy about him and being with him. He's a very good coach and I think every person will attest to that and agree with me."

In his second Pro Bowl season under O'Brien and leading the NFL with 13 touchdown catches, Hopkins definitely wants the coach back.

"Bill's a great guy, great coach," Hopkins said. "Everybody in this locker room loves him, so why not?"

It's not up to the players, though. Ultimately, what happens will come down to what McNair thinks is in the best big-picture interest of the organization.

McNair told The Chronicle after last season that he would sit down with O'Brien after this season and see how he feels, including whether the Massachusetts native wants to return. During this season, McNair expressed excitement about the future with Watson as the centerpiece of a rejuvenated offense.

As for O'Brien, he reiterated this week that he wants to continue coaching the Texans and will never quit.

"I like Bill as a coach, I'll say that, but that isn't on me to make those decisions," Clowney said. "You have to talk to those guys. I'm here to play football. For sure, I like Bill."