Despite losing three games to the New York Yankees in his team's highest-profile test this season, Davey Johnson felt good about the Washington Nationals' performance.

One thing, however, was nagging him after the Yankees completed their sweep with a 4-1 win Sunday — the offensive struggles of third baseman Ryan Zimmerman.

"What really concerns me is we've got to get Zim going," Johnson said. "We've got to get Zim to a happy place."

Zimmerman went 0 for 4 in the game and 1 for 13 in the series to drop his average to .229. His only hit came in his first at-bat on Friday and he is now 4 for 33 in his last eight games.

"Obviously I'm not doing as well as I want to," Zimmerman said. "Anytime you're not getting hits like that something has to change. I've got to keep working hard and doing the things I've done my whole career and it'll turn around."

Zimmerman missed 13 games earlier this year with a shoulder injury, but he said he's not feeling any lingering problems. Instead, he said he'll keep grinding until things turn around.

"You have a couple good games in a row and you get going, it snowballs and you get back on track," Zimmerman said.

The Nationals remain in first place in the NL East, four games clear of the Atlanta Braves, despite hitting a buzz saw in New York. Washington was swept for the third time this season — the first at home — and scored only six runs in the three games.

The Yankees won their ninth straight and maintained a 1½ game lead over the Baltimore Orioles in the AL East. The series drew the eighth, ninth and 10th largest crowds in the 4½-year history of Nationals Park, with fans in pinstripes trying to outshout the locals in red.

"That's the one good thing that came this weekend," said Adam LaRoche, who homered and doubled. "That's about as close to a playoff atmosphere as you're going to get. ... You get the place packed, people going crazy and obviously it draws a lot of media attention. It'll be good for these guys, especially the young guys, to get used to that."

Ivan Nova (9-2) shut down the Nationals, giving up seven hits and a run in an efficient, mostly trouble-free 7 2-3 innings, keeping him unbeaten in his last 15 road starts — a streak that's been going for more than a year.

Washington's only run came when LaRoche led off the second with his 12th homer. LaRoche also doubled to lead off the fourth, but he didn't have the speed to score on Ian Desmond's single to right and was left stranded by an inning-ending double play.

Nineteen-year-old Bryce Harper, who went 0 for 7 with five strikeouts in Saturday's 14-inning loss, rebounded with a double and a single, although he still wasn't pleased after the game.

"We lost, so I'm not very happy about that," Harper said.

Edwin Jackson (3-4) was constantly having to battle, allowing seven hits with three walks over six innings. The Yankees loaded the bases with one out in the first, but scored only one run on Mark Teixeira's sacrifice fly. Jackson also pitched out of a second-and-third, one-out jam in the sixth.

"It's not like we came and got blown out every game. For the most part, every game was pretty close," Jackson said. "We still feel comfortable, we still feel like we can come out and continue to win."

Curtis Granderson homered off Jackson in the fifth to break a 1-1 tie. Cano made it a two-run cushion in the seventh off Tom Gorzelanny.

The Yankees picked up another run in the seventh when Teixeira doubled and eventually scored on a passed ball by Nationals catcher Jhonatan Solano, who had another passed ball later in the inning.

Nova was pulled with two outs and a runner on base in the eighth. Boone Logan finished the inning, and Rafael Soriano pitched a perfect ninth for his 13th save.

NOTES: The sweep leaves the Cincinnati Reds (7-5) as the only major league team with an all-time winning record against the Yankees. ... Desmond booted a grounder in the fourth, giving him an error in each game of the series. ... The Nationals designated struggling reliever Brad Lidge for assignment. Lidge, 35, went 0-1 with two saves and a 9.64 ERA in 11 appearances and gave up five runs in the first two games of the Yankees series. ... Ryan Mattheus, activated to take Lidge's roster spot, got one out Sunday.