ARLINGTON, Texas (TNS) — This place should be filled with music and laughter and swagger, but instead all you hear is the white noise from the showers around the corner. These players should be winning and joking, but instead they keep their heads down, their words in mostly hushed tones.

This is a locker room rocked, or at least uncertain, the Chiefs’ five wins to start the season now stuck in the mud of just one win in four after a 28-17 loss to the Cowboys here on Sunday.

The Chiefs are 6-3, which is an objectively good record, but trends matter too, so by the time the men in this room play again it will have been 20 days since their last win and 42 since they last won two in a row.

This team has the highest expectations of any the franchise has fielded in years, at least a decade, and right now a group that wants to believe it will play in the Super Bowl cannot stop anything not quarterbacked by Trevor Siemian.

“We need to regroup,” linebacker Derrick Johnson said. “We just gotta get better, man. Gotta get better. And I’m talking defensively.”

This was the Chiefs’ worst game of the year, the first time they didn’t have a chance at the end, and enough was amiss that we can all pick our pet peeve and none of us would be wrong.

The offense was pushed around by an average defense, with nearly half of the Chiefs’ points and 20 percent of their yards coming on a video-game catch and run by Tyreek Hill at the end of the half. They are too talented and finally too healthy for this, and if you want to point the blame there, fine, have at it. You won’t be wrong.

But the bigger problem is the other side, with a defense built on creating turnovers and stiffening in the red zone that at the moment is neither creating turnovers nor stiffening in the red zone.

They want to attack the quarterback and bend but not break, but at the moment they are hardly bothering the quarterback and are both bending and breaking.

“We struggle with the run,” said Tamba Hali, who played for the first time this season. “We just need to play the whole game. I think there are times we just relax, from what I saw.”

This defense should be better than this, and we can talk about the reasons it’s not. This group was built largely around three terrific playmakers. Eric Berry is out for the year, Justin Houston’s health is week-to-week, and Marcus Peters has been mostly good in coverage but also unchallenged because no second cornerback has emerged.

Berry is a football ninja, able to support the run while still playing the pass, and with him injured teams have often targeted his successor, safety Daniel Sorensen. The Chiefs tried using more base defense against the Cowboys, with an extra linebacker. This strategy saw some success in the first half, but little in the second, and besides, when the Cowboys went to three wide receivers the Chiefs responded with an extra defensive back.

Part of the problem with defense is that by nature you are usually reacting. This means that teams know they can isolate the Chiefs’ weakest personnel against the run.

But it’s not just the run. The most damning series came toward the end of the first half. The Chiefs pushed the Cowboys back to a third and 15 from their own 13 and promptly threw up on themselves — Dez Bryant got behind the coverage to convert a first down, and then the Chiefs just blew one to allow Terrance Williams to go 56 yards.

From third and long inside their own 20 to first and goal from the Chiefs’ 10 — all in less than a minute.

This continues a bizarre and troubling trend — the Chiefs entered the weekend worst in the league against third and long.

They’re too good for this. They have too many good players, and have been together too long. They’ve ranked no worse than seventh in points allowed the last four years, but they are now in the bottom third of the league.

With the notable exception of the Dick Vermeil years, Kansas City is used to watching diesel truck defense ruined by tricycle offense, so it’s a weird thing to be wondering if the defense is going to screw up an otherwise promising season.

“Not good enough,” Johnson said. “Just an average game for us. Defensively, when we play an average game, we usually get beat. Just average.”

The fixes are harder than the diagnosis. Over and over in the locker room, you can hear guys saying they have all the pieces they need. You will hear support for defensive coordinator Bob Sutton. And they are undoubtedly right, to a certain extent.

This group can be better. It should be better. But the problems are in everything they need to be better, and the unintended consequences of those actions.

Peters needs to make plays, and he needs to cover better, but he also needs opportunities, which means the other corners need to be better. Houston needs to be dominant, but he needs to be healthy. They need to stop the run, but too much focus there leaves them vulnerable in the back.

The simplest solution is up to both the coaches and players. Now more than ever, Sutton needs to use creative blitzes — “games,” in the sport’s jargon — to help get his players in rhythm and the quarterback out of it. That was particularly evident on the third and 15 conversion to Bryant.

The players need to be better on their end, too. The loss in Oakland, in particular, was just littered with breaks in execution. Here in Dallas, Eric Murray jumped a route and should’ve had a pick-six, but the ball appeared to go through his arms for a completion and Dallas first down. In that same series, the Cowboys converted on second and 15 after Williams caught the ball against soft coverage and then ran around Kenneth Acker, who fell down, for a 27-yard gain that set up their first touchdown.

These are basic failures.

All teams have flaws. That’s true about sports in general, and the NFL in particular. It’s easy to forget that other teams those flaws, too. That’s a basic truth about following one team closely.

But Super Bowl teams don’t have these types of flaws. And this has always been a season that will be fairly judged on a higher standard.