 -- Something is rotten with the Houston Rockets.

Picked to contend in the Western Conference after adding point guard Ty Lawson to the returning core of the team that reached the conference finals a scant nine months ago, the Rockets have instead flopped. A 4-7 start cost head coach Kevin McHale his job, and the new voice of replacement J.B. Bickerstaff hasn't helped.

After briefly appearing to right the ship at 25-22, Houston heads into the All-Star break having lost six of its past eight games and with both players and Bickerstaff sounding ominous notes about the team's chemistry.

"We're broken. It's that simple," Bickerstaff said after Wednesday's loss to the Portland Trail Blazers, which pushed the Rockets out of the eighth and final seed in the West playoffs at the break. "We're a broken team, and we all need to use this break to figure out how we're going to impact change. If we don't want to impact change, then we need to be made aware of that, too, and we'll go in a different direction.

"We can't continue to go out and play this way. It's easy to see it's a fragmented bunch. You can't win that way."

As Bickerstaff hinted, Houston GM Daryl Morey could shake up the roster with the trade deadline a week away. Reports Thursday indicated the Rockets have been calling teams about trading center Dwight Howard, who can become an unrestricted free agent this summer.

But mounting evidence suggests that the real problem isn't Howard or any of Houston's role players. Instead, it's the one player the Rockets presumably wouldn't consider trading: superstar shooting guard James Harden.

As preposterous as it sounds, trading Harden might be the only way to fix a broken team.

Same players, different results

The chemistry issues are confusing because Houston's roster is largely the same as last season's, when the team won 56 games and two playoff series. After Morey reacquired Josh Smith in a January trade, the only Rockets player who saw more than 50 minutes of action in the 2015 postseason and is now elsewhere is backup point guard Pablo Prigioni.

With the benefit of hindsight, the calculated gamble Houston made trading for Lawson looks like a mistake. After spending part of his summer in a court-mandated alcohol rehab program after multiple DUIs, Lawson hasn't been the same player he was with the Denver Nuggets. He quickly lost his starting job, and according to NBA.com/Stats data tracking the Rockets have been outscored by 6.7 points per 100 possessions with him on the court -- a similar net rating to the imploding Phoenix Suns (minus 7.3 points per 100 possessions).

Nonetheless, Houston's issues go far beyond Lawson. With him on the bench, the Rockets are outscoring opponents, but by a middling 1.2 points per 100 possessions -- far worse than last season's plus-3.7 mark.

Lawson also can't be blamed much for Houston's defensive decline. The Rockets have allowed a 106.1 defensive rating with the struggling point guard watching from the sidelines, good for a tie for 23rd in the league defensively. (Houston is 28th overall at 106.4 points allowed per 100 possessions, ahead of three teams -- the Brooklyn Nets, L.A. Lakers and Suns -- with a combined 39 wins at the break.)

For all Harden's offensive prowess and the Rockets' vaunted emphasis on smart shot selection, last season's team won with stingy defense. Despite playing 41 games without Howard, Houston allowed just 100.5 points per 100 possessions in 2014-15, good for sixth-best in the league.

Taking a closer look at what's wrong with the Rockets' defense means we have to point the finger at The Beard.

Harden's disappearing defensive effort

Two seasons ago, Harden's defense made him a laughingstock of the Twitterverse. The mockery, in combination with Houston's devastating loss to the Portland Trail Blazers in the opening round of the playoffs, seemed to light a fire under Harden. His defensive effort improved to acceptable and possibly even good levels, a major reason the Rockets were so effective as a team defensively.

Whatever the reason -- Harden has pointed to an offseason ankle injury, which McHale said this week on TNT's "Inside the NBA" caused Harden to come into camp overweight -- that improvement has not carried over this season.

Houston has allowed 4.4 more points per 100 possessions this season with Harden on the court compared to when he's on the bench, undermining much of his offensive value. The Rockets' defense is even worse when Harden doesn't have Howard protecting the rim behind him. Houston's 108.7 defensive rating in those 909 minutes would be the league's worst, per NBA.com/Stats tracking. The Rockets defend at almost a league average clip when Howard plays but not Harden.

Houston's poor transition defense can also be traced to Harden's presence. Per NBA.com/Stats, the Rockets allow 14.7 fast-break points per 48 minutes with Harden on the court (a rate that would be sixth worst in the NBA) and just 11.9 with him on the bench (13th best in the league).

Quantifying individual defense is challenging because defense is a team effort, but SportVU tracking on NBA.com/Stats does match the observation that Harden's lax defense is giving up open shots. Opponents have made 46.7 percent of their attempts with Harden as the primary defender, as compared to 44.7 percent overall on the same type of shots. Last season, players shot 1.6 percent worse than their usual average with Harden as a primary defender.

Harden argued early this season that he was playing too many minutes, surely a factor in his effort level on defense. But we know that he's capable of carrying a heavy offensive load and still competing on D because he did it last season, when he finished second in MVP voting. And that's precisely what makes the idea of trading Harden so difficult to swallow.

Morey's dilemma

Any moves the Rockets make at the deadline -- involving Howard or any of his teammates -- are likely to be futile if Harden is the real underlying issue.

Regardless, Houston has a good chance of claiming a playoff spot because the Blazers have a more difficult schedule in the second half of the season. Simulations based on ESPN's Basketball Power Index show the Rockets reaching the postseason about two-thirds of the time.

But as a likely low seed, Houston is no longer a title contender. The Rockets will probably have to go through Golden State, San Antonio or Oklahoma City just to win one round, never mind getting to the conference finals again. Since his goal is to win a title, that leaves Morey in a tough spot.

Potential Harden trades

There's no single obvious trade fit for Harden, but the star-hungry Boston Celtics could offer All-Star Isaiah Thomas to replace his shot creation, cap relief with David Lee's expiring contract and perhaps one of the coming picks they're due from the Brooklyn Nets to give the Rockets a chance at another star.

If Houston believes D'Angelo Russell has superstar potential, the Lakers would have to consider giving him up to get Harden, an L.A. native.

And there are at least two lottery teams who seem hungry to get better now. The Denver Nuggets could build a package around Danilo Gallinari, Gary Harris and draft picks. Likewise, the Orlando Magic could offer Victor Oladipo, Aaron Gordon and picks.

But none of those packages deliver the Rockets a surefire top-10 player, which is where Harden ranks at his best. Morey famously worked for years to acquire the picks and young players necessary to snag Harden from the Oklahoma City Thunder, the move that enabled Houston to sign Howard and build the team that reached last season's conference finals. Dealing Harden for anything less than another superstar could leave the Rockets back in a similar spot to before they got him.

At the same time, no matter his offensive success, Harden simply isn't performing like a superstar or a top-10 player right now. If his current frustration isn't enough to get Harden to expend effort on defense, who's to say that he will be able to summon it up in the future?

If he can't, Houston is better off grabbing value now while other teams believe they can get last season's version of Harden.