The Cowboys' late rally fell short when kicker Brett Maher missed a 52-yard field goal attempt off the left upright as time expired.
Here are NBC 5 Cowboys Insider Jean-Jacques Taylor's 10 thoughts on the loss.
1. Long snapper L.P. Ladouceur has played in 212 games for the Cowboys. He's been penalized five times -- none since the playoff loss to Green Bay at end of the 2014 season. He was also called for a false start in that game.
His five-yard penalty for a snap infraction turned a 47-yard field goal attempt into a 52-yard attempt.
Maher's kick banged off the left upright as time expired, giving Washington a three-point win.
2. Ezekiel Elliott had the second-worst rushing game of his career with 34 yards on 15 carries. His longest run was six yards, which means the Cowboys spent a lot of time in second-and-long. Washington has not allowed a run of more than 18 yards this season.
3. Maher had made 16 consecutive field goals -- he hadn't missed since the opener against Carolina -- and he had kicked a game-winner to beat Detroit.
But his 52-yard attempt against Washington looked off from the moment he kicked it. Most of his kicks this season have been down the middle with good height. His kick Sunday wobbled from the start.
4. Dak Prescott had an up-and-down game. He passed for a season-high 273 yards and a touchdown, and he added 33 yards rushing and another score.
He also lost two fumbles -- one was returned for a touchdown -- but he was terrific in the last five minutes as the Cowboys nearly rallied from a 10-point deficit.
5. Washington won because it controlled both lines of scrimmage. Adrian Peterson rushed for 99 yards on 24 carries and he had a couple of long runs called back. Washington's defensive line shut down Elliott and sacked Prescott four times. They also hit him eight times and forced at least three holding penalties.
6. Why did it take Dallas more than three quarters to find Cole Beasley, who was unstoppable on the final couple of drives? Too many times, the Cowboys take what the defense gives them instead of taking what they want.
7. Rookie Michael Gallup continues to improve every week. He had three catches for 81 yards, which were both career highs. He also scored his first touchdown on a 49-yard catch.
8. DeMarcus Lawrence didn't have a sack, but he was a force with seven tackles, three for loss and a quarterback hit.
9. The Cowboys' average starting field position was their own 21. Only one of their 11 possessions started outside their 26-yard-line and that was their final possession. Washington's average starting field position was its 33.
10. Prescott ran six times for 33 yards, but he took a hard hit to the head late in the first half while he was trying to dive out of bounds, which reminded everyone just how risky it is every time he takes off. He also had an awkward slide in the first quarter that left him limping.