Jamison Crowder tipped a pass that led to an early interception and then fumbled a punt return. (Jonathan Newton/The Washington Post)

The miscues mounted in calamitous fashion, snowballing within minutes. And in the midst of it all was Jamison Crowder.

Finally healed from a lingering hamstring injury, Washington’s diminutive wide receiver had been a much-needed safety net for the Redskins’ offense of late. And with so many weapons lost to injury in recent weeks, he again was expected to be a trusted asset for Kirk Cousins on Thursday night.

But instead Crowder proved to be a liability early on against the Dallas Cowboys.

In a game Washington needed to win to keep its improbable playoff hopes alive, Crowder was one of several culprits who thwarted their own momentum en route to a 38-14 letdown loss at AT&T Stadium.

The defeat dropped the Redskins to 5-7 and all but assured that they will miss the playoffs.

There were plenty of mental lapses (three penalties) and poor decisions (three fumbles) for the Redskins in the first half. While there was more than enough time to atone for the mistakes, Washington couldn’t get out of its own way when it mattered most.

Crowder’s dropped red-zone pass in the first quarter resulted in Cousins’s seventh interception of the season. Then Crowder compounded the issue later in the first quarter when he fumbled a punt return.

“It’s human nature to get down on yourself,” he said in a near-empty visitors locker room afterward. “But you have to keep telling yourself to keep playing. Ride the wave.”

It was an uncharacteristic showing for the typically sure-handed Crowder, who had garnered praise from his head coach for being a vital piece of their offense.

“Jamison is doing a great job,” Jay Gruden said this past week of Crowder, who was coming off the best four-game stretch of his career: 27 receptions for 412 yards and a touchdown. “He’s really starting to show what he is all about the more opportunities he gets.

“Sometimes he gets lost in the mix, but now he is becoming a feature-type guy and he is taking advantage of every ball that is coming his way. Great separation, strong hands, good running after the catch. So he is going to be critical down the stretch for us to be successful. . . . We still have to stay balanced and keep everybody involved, but Jamison will be a key component.”

For that reason, the timing of Crowder’s blunders was even more surprising.

The Redskins seemed poised to put points on the board on their second offensive drive as Cousins fired a pass to Crowder from the Dallas 16-yard line. The ball deflected off Crowder’s hands right into the path of Cowboys safety Jeff Heath, who snagged the ball at the 2-yard line and scampered 14 yards in the opposite direction.

“It just went through my hands, and [No.] 38 made a good play,” Crowder said, matter-of-factly.

The Redskins forced a punt, but Crowder’s fumbled return gave the ball back to Dallas at Washington’s 43-yard line. “One of their players just knocked it out my hand and made a good play,” Crowder explained.

And yet, thanks to their defense, the Redskins escaped the first quarter unscathed and the score tied at 0.

The evening could have been worse for Crowder had the officials not ruled him down by contact late in the second quarter after he caught a 5-yard pass from Cousins and then lost the ball at the end of the play.

The night wasn’t completely bad, though.

With less than two minutes left in the first half, Crowder turned a short catch into a 33-yard, third-down gain that helped set up Ryan Grant’s 20-yard touchdown, which pulled the Redskins to within 17-7.

It’s unclear whether the pass was even intended for Crowder. “I just caught it and ran,” he said.

A visibly irritated Gruden kept his remarks brief postgame, but in recent days he had highlighted Crowder’s improved play since his return from the hamstring injury.

“He definitely looks crisper in and out of his breaks” Gruden told reporters after a recent practice. He “has looked crisper the last four or five weeks quite frankly and has been producing at a very high clip, which is exciting.”

But that high production never materialized in front of a prime-time audience Thursday night. Crowder finished with five catches for 67 yards.