Kirk Cousins watches from the sidelines with safety D.J. Swearinger as quarterback Colt McCoy plays the final possession Thursday night. (Jonathan Newton/The Washington Post)

With the NFL playoffs at stake, the Washington Redskins turned in a flat, sloppy performance against an NFC East rival and saw their slim postseason hopes crushed in the defeat. That was Week 17 last season, when the Redskins fell to a New York Giants team that already had clinched its playoff berth.

This season, the playoff reckoning came sooner, in Thursday’s nationally televised, Week 13 clash at the Dallas Cowboys — a game between NFC East rivals with matching 5-6 records, each clawing to get to .500 and preserve a slim hope of a wild card.

In many ways, the Redskins’ 38-14 loss was reminiscent of their deflating finish to 2016. With so much at stake Thursday against the Cowboys, the Redskins committed four turnovers, dropped potential touchdown throws and let a pair of backup running backs gash them for 148 yards to snuff out their playoff hopes as they fell to 5-7 overall, 1-4 in the division.

Moreover, the Redskins’ third loss in their past four games breathed life into the moribund Cowboys, whose owner, Jerry Jones, called it an “inspirational” victory under must-win conditions and reveled in the 127-yard rushing performance of Alfred Morris, Washington’s castoff Pro Bowl back.

Speaking to reporters Friday afternoon, Redskins Coach Jay Gruden insisted that his team was ready when it took the field at AT&T Stadium, pointing to the four consecutive three-and-outs that his defense forced from the Cowboys.

The problem, the coach said, was the uncharacteristic errors and missed opportunities. Among them: wide receiver Jamison Crowder letting a potential touchdown pass slip through his hands; a fumbled punt return; an 83-yard Dallas punt return for a touchdown; and a defense that wore down, allowing 21 points in the fourth quarter.

“I wouldn’t say we weren’t ready to play,” Gruden said. “I think, one, they made a couple plays, and, two, we didn’t make the plays we normally make.”

But the morning after, the harsh reality of another disappointing regular season was tough for Redskins fans to take. And there was a familiar ring to the gripes aired on social media and talk radio.

Did Gruden have his team prepared? Did players give it their all? Why, yet again, did an NFC East rival bring more fight to a must-win game than the Redskins?

“It’s devastating,” Redskins cornerback Bashaud Breeland said in a largely silent locker room Thursday night. “A game that could help us clinch a playoff spot, and we are going to lay an egg like this. It hurts.”

Unlike last season, when coaches and players scattered after their postseason hopes died with the Week 17 loss to the Giants, this season’s squad has four games remaining: at the Los Angeles Chargers, back-to-back home games against Arizona and Denver; and a finale at the Giants on New Year’s Eve.

Gruden said Friday the team would evaluate on a case-by-case basis whether to shut down ailing starters such as left tackle Trent Williams and tight end Jordan Reed for the balance of the season or continue working to get them back in the lineup.

“We obviously don’t want to hurt anybody’s future — if it’s a chance to injure themselves long term,” Gruden said. “But, you know, if it’s just a nagging ankle sprain or something like that where they just can play through it, then they’ll play through it.”

Even before players boarded the flight Thursday night, quarterback Kirk Cousins insisted that the commitment to winning wouldn’t wane.

“We are all professionals, and we are all being evaluated every single game and every single practice,” said Cousins, 29, whose future in Washington will dominate the offseason narrative. He’s due to become a free agent in March after playing the past two seasons under the NFL’s franchise tag, a costly mechanism for keeping highly valued players from leaving once their contracts expire.

Despite Cousins’s back-to-back 4,000-plus yard passing seasons and a body of work that places him among the top 10 NFL quarterbacks, it’s unclear how much team owner Daniel Snyder and team President Bruce Allen value him. Enough to extend a market-rate, long-term contract that would persuade him to sign? Enough to use an unprecedented third franchise tag (for a one-year salary of $34.5 million) to force his return? Or just enough to risk losing him to a team that outbids for his services via the NFL’s transition tag?

But on Friday, it was Gruden, Allen and Snyder who were the focus of the heated debate over the Redskins’ latest defeat.

“We’re taking calls on the Redskins disaster!” an announcer said on the Snyder-owned ESPN 980 radio station. The tenor was much the same on 106.7 The Fan’s “Grant and Danny Show,” which served as part therapy session, part gripe session for Redskins fans alternately gutted, disgusted, disillusioned and agitating for change.

The Redskins had been favored at Dallas for the first time since 2004. But after an encouraging start, they undercut themselves while resurrecting the foundering Cowboys, who entered on a three-game losing streak that had seen them outscored 92-22.

Dallas regularly got hits on Cousins and sacked him four times. Morris ran down the throat of a gassed Redskins defense, gaining 89 of his 127 rushing yards in the second half.

An injury-ravaged Redskins team that has been pieced together with backups failed to deliver. Crowder committed two turnovers in a two-minute span. Swing tackle Ty Nsekhe struggled in pass protection, switched from left guard to right tackle once starter Morgan Moses exited with a sprained right ankle. And a defense that impressed early in the season has now given up 38, 34 and 38 points in three of the past four games.

Thursday’s loss brings Gruden’s record in Washington to 26-33-1, raising questions about his job security even though the Redskins granted him a two-year contract extension in March (taking him through 2020). It was a move that smacked more of an inducement to persuade Cousins to sign a long-term contract than it did an endorsement of the coach’s ability.

Could Snyder fire Gruden after four seasons? It might be imprudent financially, but Snyder has cost himself millions before in firing coaches in a fit of pique.

But if Snyder sent Gruden packing, he logically also would have to sever ties with Allen, who was the driving force behind tapping Gruden to succeed the ousted Mike Shanahan as coach. Allen’s other major personnel move — hiring general manager Scot McCloughan in January 2015 — lasted less than two years into a four-year deal.

But if Snyder and Allen want to make a case for retaining Gruden, they can surely do so. Cousins has made impressive strides under Gruden’s tutelage. And this season’s losses can be attributed, at least in part, to the raft of injuries along the offensive line; the half-dozen games without Reed, a focal point of offense; the second consecutive first-round draft pick (defensive lineman Jonathan Allen) to miss the bulk of his rookie season because of an injury.

Cousins, for one, said he’s focusing on finishing strong. “There’s a lot to be done in the month of December, to walk away from the season and feel really good about where we are as an organization and where we are headed.”