The Redskins (3-2) allowed 108 points in their first four games and came in with the league's 29th-ranked defense. In this one, Washington gave up a touchdown on the game's opening drive and smothered the Ravens (3-2) the rest of the way.
"The defense stepped up," coach Jay Gruden said. "The first drive was a little scary. Here we go again. But we came back, took it personal and played well."
The game wasn't decided until the final minute, when an apparent 23-yard touchdown catch by Baltimore's Breshad Perriman was overturned by replay. Perriman got his right foot down in the end zone, but his left foot was out of bounds.
That put an appropriate end to a miserable day for the Ravens offense, which was limited to 125 yards after halftime.
"We can't play like that and win," coach John Harbaugh said. "We have to be better than we were today."
Crowder scored Washington's first TD with a sensational run through the middle of the Baltimore punt return team in the second quarter.
The Redskins went ahead 13-10 in the third quarter with a 50-yard drive following a wind-shortened punt by Sam Koch. Cousins connected with Crowder for 23 yards before lofting a 21-yard pass to Pierre Garcon, who got behind Jimmy Smith and caught the ball in the left side of the end zone.
The definitive momentum shift occurred minutes later. With the Redskins operating from near their own 3, Ravens linebacker C.J. Mosley intercepted a pass by Cousins at the 13, but lost control of the football while reaching for the end zone. The ball rolled out of bounds in the end zone for a touchback, and the Redskins subsequently moved 72 yards for a field goal and a 16-10 lead.
Cousins went 29 for 41 for 260 yards. But it was the defense that won the game for the Redskins.
Washington repeatedly frustrated Baltimore quarterback Joe Flacco, who was 30 for 46 for 210 yards and sacked three times.
The Ravens have lost two in a row -- both at home -- after opening with three straight wins. All of their games have been decided by six points or fewer.
Baltimore scored a touchdown on its opening possession for the first time this season, on a 7-yard pass from Flacco to tight end Crockett Gillmore.
Crowder responded with the Redskins' first punt return for a touchdown since 2008. But the conversion attempt clanged off the left upright.
A field goal by Justin Tucker made it 10-6 in the second quarter. The Ravens had a chance to add to the lead after recovering a fumble by Matt Jones at the Washington 15, but a fake field-goal attempt went awry.
Playing in a stiff wind, neither team got much from its kicking game. Dustin Hopkins missed an extra point for Washington and came up short on a 56-yard field goal try.
Baltimore opted to try a fake field goal in the second quarter, and failed. Later, Koch got off a 36-yard punt that didn't rise more than 20 feet off the ground.
Ravens: Baltimore played most of the game without receiver Steve Smith, who sprained an ankle late in the first quarter. The Ravens also lost OT Rick Wagner (thigh) and endured a second straight game without rookie tackle Ronnie Stanley (foot).
Ravens: CB Shareece Wright was inactive. He started the first four games, but struggled in the last three. Ravens say Wright had back spasms recently, but he practiced all week.
Redskins: Jones ran for 31 yards on 14 carries and lost a fumble for the first time this season.
Ravens: Terrance West peeled off a 35-yard run on the opening possession, Baltimore's longest of the year. He finished with 95 yards on 11 carries.
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