PHILADELPHIA -- Aaron Altherr was on the bench all day Sunday, a chilly and windy day at Citizens Bank Park. Once he entered, he only needed one pitch to give Philadelphia Phillies a jolt.

Altherr blasted a pinch-hit, three-run home run to even the score in the bottom of the eighth and the Phillies won in the 10th on a walk-off sacrifice fly by Freddy Galvis in a 6-5 win over the Washington Nationals.

Galvis finished the day with three RBIs.

With one away in the 10th, Galvis took a first-pitch slider from Blake Treinen (0-1) to deep center field. Michael Taylor caught the liner and never had a chance to throw out Odubel Herrera at the plate.

Herrera led off the 10th with a check-swing double down the left-field line. Altherr was intentionally walked before pitcher Vince Velasquez came off the bench to attempt a sacrifice bunt that turned into a bunt single to load the bases. Treinen struck out Andres Blanco but couldn't get out of trouble.

"We need a win like this," Galvis said.

The Phillies (13-17) snapped a five-game losing streak while halting a four-game win streak for the Nationals (21-10), baseball's best team.

Hector Neris (1-1), Philadelphia's closer, got the win after throwing two shutout innings.

Altherr (sore left wrist) missed the game Saturday and wasn't in the starting lineup Sunday.

"I figured with the day off tomorrow, today would be a good day to give him another a day off, knowing he was available to pinch-hit," Phillies manager Pete Mackanin said. "It worked out well."

It worked out well because the Nationals have a problem.

For all of Washington's early-season success, its bullpen has been miserable. It entered Sunday ranked 26th in bullpen ERA (5.32). Sunday's implosion wasted a good start from Tanner Roark.

Matt Albers came on for Matt Grace in the eighth with two runners on. He tried to get a first-pitch slider past Altherr but missed his spot.

"I was looking fastball and he hung a slider over the middle and I was able to recognize it pretty early and put a good swing on it," Altherr said.

Two of the runs were charged to Grace on Altherr's homer.

"That's the first mistake he's made on a slider," Nationals manager Dusty Baker said of Albers, who entered Sunday having not allowed a run. "It's a mistake (Altherr) didn't miss."

With closer Shawn Kelley (back) on the disabled list, the Washington bullpen is depleted. Treinen, the Opening Day closer, had his ERA jump to 9.22.

"The 10th was started with a check-swing double," Baker said. "There's not a whole bunch you can do about that. Perfectly executed bunt ... we didn't get an out. The life of a reliever is you have to forget yesterday."

Philadelphia nearly won the game in the bottom of the ninth.

Albers allowed the first two batters to reach base and Baker summoned lefty Enny Romero, who struck out Phillies catcher Andrew Knapp before allowing an infield single to Brock Stassi to load the bases for Cesar Hernandez. Romero got out of the jam with a groundout and a pop-up to send the game to extra innings.

But Neris sent the Nationals down in order to get the Phillies back to the plate in the 10th.

Philadelphia's win spoiled a big day at the plate for Nationals outfielder Jayson Werth, who homered twice and finished a triple shy of the cycle in a four-hit effort.

With Washington trailing 2-1 in the top of the fifth inning, Werth took a Jeremy Hellickson fastball deep to left for a go-ahead homer.

Werth's first-inning home run gave the Nationals a 1-0 lead.

Werth's last three multi-homer games have come against Philadelphia. His 22 lifetime home runs against the Phillies, the team he played with for four seasons, are the most he's hit against any opponent.

"I've always liked hitting here, liked playing here," Werth said. "It's a hitter's park, good batter's eye."

Roark, who didn't give up a hit until the fourth inning, threw six innings of two-hit baseball. He allowed two unearned runs, walked three and struck out five.

The Nationals gave him a pair of insurance runs in the seventh off Phillies reliever Jake Thompson to make the score 5-2. The insurance was for naught.

The Phillies took a 2-1 lead in the fourth on a two-run double off the bat of Galvis. The runs weren't charged to Roark since the inning was extended thanks to an error by shortstop Trea Turner.

Hellickson lasted 4 2/3 innings. He allowed three runs on five hits (two home runs) while walking three. He struck out four.

NOTES: Washington OF Bryce Harper (groin) missed his third consecutive game. ... Philadelphia's pitching staff has now surrendered 48 homers this season, the most of any team in Major League Baseball. ... The Phillies have an off-day Monday before hosting Seattle for a two-game set beginning Tuesday. ... The Nationals head to Baltimore for the beginning of the annual Beltway Series, a two-game, home-and-home series with the Orioles starting Monday.