It was a tough blow to take for a Redskins team desperate to end the playoff hopes of its fiercest rival. Washington enjoyed some fine moments on both sides of the ball but too often committed elementary mistakes.
The Redskins were also once again harmed by dire special teams play. That and some questionable play-calling on defense headline the team's takeaways from the penultimate week of the season.
Cousins was smart and efficient for most of the game.
Kirk Cousins enjoyed a mostly positive second game in relief of Robert Griffin III. His most impressive qualities were efficiency and variety.
Cousins again spread the ball around. He connected with six different receivers, even if he did favor Pierre Garcon more than any other.
Cousins also showed a nice knack for settling for intermediate gains whenever the long ball was unavailable. He frequently checked the ball down against the deep-zone shells the Cowboys favor.
Cousins stayed patient against a scheme that dares quarterbacks to take risks. This is not a trait Griffin has yet mastered.
That speaks to the main difference between the two quarterbacks. Griffin is the superior athlete and more dynamic playmaker.
But while he can't match Griffin's physical skills, Cousins has the better intangibles.
Pierre Garcon has become a dominant player at his position.
Pierre Garcon has proved those, including this author, who doubted whether he was a legitimate No.1 receiver spectacularly wrong this season.
Garcon has joined the ranks of the elite during a record-breaking campaign. His numbers against the Cowboys were simply awesome.
He made 11 catches for 144 yards and a score. Garcon moved across the formation at will and tormented every level of the Dallas pass defense.
Those efforts helped him establish a new Redskins single-season record for receptions in a season. That achievement is cause for mixed emotions after defeat, as noted by Rich Tandler on his Real Redskins blog:
With about six minutes left in the third quarter, Garçon caught a 19-yard pass from Kirk Cousins, his 107th catch of the year. That broke the Redskins record set by Hall of Fame wide receiver Art Monk, who had 106 catches in 1984. The reception set up an Alfred Morris touchdown that gave the Redskins a 20-14 lead over Dallas.
But when it was over, the Cowboys walked off the field with a 24-23 win, and Garçon was not happy despite his accomplishment.
His obvious disappointment aside, Garcon should take great pride from the record. It is one that reveals his maturation into a complete receiver.
Garcon still has the speed to stretch the field, but he has become dominant underneath. Few, if any receiver in the NFL, is better after the catch than the tough and resourceful 27-year-old.
The direction of the offense remains shaky, given the quarterback changes and uncertainty over the future of the coach. But in Garcon, the Redskins now have an obvious focal point for their passing attack and a true game-winner.
Fred Davis saw only one pass come his way against Dallas.
As well as Garcon is playing, no other member of the receiving corps is doing enough to damage defenses. Without rookie tight end Jordan Reed, there are simply not enough competent weapons around Garcon.
In some cases, talented playmakers are being wasted. Reed's replacement, Fred Davis, saw only one pass come his way for the second straight week.
It makes no sense not to use an athletic "move" tight end like Davis more often. The same is true for running back Roy Helu Jr.
He is a very effective receiver out of the backfield, although you would hardly know it. Helu received just two passes against the Cowboys and has just 27 catches this season.
That is a chronic waste of one of the team's most threatening weapons with the ball in his hands. Not using players like Davis and Helu more often makes even less sense, considering the lack of a credible second wide receiver.
Veterans Santana Moss and Josh Morgan have been left on the sideline for most of the season. Admittedly, neither has impressed with the limited opportunities they have had.
Young players like Aldrick Robinson and Nick Williams are either ignored or struggle to capitalize when they get their chances.
That failure to capitalize plagued most of the Redskins' pass-catchers in Week 16. Aside from Garcon, nobody could make the first man miss and produce extra yards.
While the defense needs the most work this offseason, more pieces have to be added to the offense.
When Brian Orakpo left the field, the pass rush fell flat.
Brian Orakpo may have been very quiet by his recent standards, but he remains essential to this team's pass rush. When Orakpo left the field in the fourth quarter, following a suspected groin injury, the Washington defense couldn't generate pressure.
Orakpo had been struggling to get around left tackle Tyron Smith, but he still stayed quick off the ball and commanded attention.
With Orakpo on the sideline, the Cowboys frequently rolled Romo out to the other side, where Ryan Kerrigan was kept in check. Romo had far too much time without Orakpo's threat.
Thankfully, Orakpo has indicated his injury is not too serious, according to CSN Washington's Tarik EL-Bashir:
Orakpo did not return to the game and declined to speak to reporters before walking out of the locker room. He did not appear to be limping. Orakpo did, however, tell a teammate that he does not believe the injury is serious.
Like Garcon on offense, Orakpo must be surrounded by more playmakers on the defensive side.
Jim Haslett made a terrible decision late on.
Jim Haslett's decision to go conservative with the game on the line shackled a defense that had made its share of big plays. Haslett had been calling many intricately designed blitz pressures that succeeded in rattling Romo.
But on the final drive, Haslett rushed only four. That gave Romo too much time to wait for receivers to break open for key catches.
The cautious and unimaginative change in style was just another example of Haslett's poor handling of the defense. He hasn't been helped by suspect personnel, but he has called too many bad games to lean on that excuse any longer.
Jarvis Jenkins and the D-line are getting pushed around too often.
The Washington defense is failing because the men up front are not winning enough of their battles. The D-line was pushed around too easily by the Cowboys.
The Dallas offensive line is a good one. Smith and Doug Free are fine tackles, and rookie Travis Frederick is a skilled center.
But there is still no excuse for the way the Redskins were manhandled most of the game. Defensive linemen are being moved off the ball too often, and there is nowhere near enough penetration.
That's why the run defense has regressed this season, evidenced by DeMarco Murray averaging 4.4 yards a carry in Week 16. If this 3-4 scheme is ever going to work, the Redskins must find some physical dominance up front.
Keith Burns' unit is a comedy of errors that shows no signs of ending.
Even in a game where it had some good moments, the Washington special teams still made its customary pair of costly gaffes.
The first was allowing a huge return from recently signed Micheal Spurlock that led to the Cowboys' opening touchdown. But things appeared to settle down for this atrocious group after that.
Returners were contained, and the Dallas offense was pinned deep more than once. But perhaps inevitably, it proved too good to be true, and the improvement didn't last.
When Cousins and the offense got the ball back trailing by a point and with barely over a minute left, a block in the back penalty made their task even harder.
There is never a good time for a penalty, but in this context, this one was a disaster. A disaster is just what this special teams unit has been under the stewardship of first-year coordinator Keith Burns.
That Burns has survived this long is nothing short of a miracle. But he surely can't outlast a much needed purge in this area during the offseason.
Mike Shanahan's team makes too many elementary mistakes.
The Redskins are 3-11 for a lot of reasons. But one of the more obvious causes is the frequency of basic errors.
Numerous calamities have cost the Redskins at key moments in too many games. The Washington Post's Dan Steinberg highlighted one such incident against the Cowboys:
Washington had a 3rd-and-goal at the 2-yard line in the first half. A false start and an illegal shift instead made it 3rd-and-goal from the 12. Then the Redskins wound up taking a timeout for good measure. They wound up with a field goal.
This kind of error-strewn football is nothing new. Mike Shanahan's team is often guilty of ludicrous penalties, a failure to even get lined up properly and an inability to protect the ball.
That is a theme that recurs every week. It hints at a chronic lack of discipline and not enough emphasis on getting the basics right.
Elementary mistakes have been the defining feature of a season that demands a major rebuild at every level of the franchise.