WASHINGTON -- Before the game, San Diego rookie manager Andy Green said his team was on one of the hardest road trips of the year in the majors.

That is hard to argue since the Padres just played in St. Louis and have two more games against first-place Washington this weekend before heading to Toronto for a series Monday.

But thanks to two home runs and four RBIs from hot-hitting Matt Kemp, the Padres snapped a four-game losing streak with a 5-3 victory Friday night over the Washington Nationals. It was the first win on the road trip for San Diego.

Kemp, after some rest during the All-Star break, has six homers in his last six games. He has 22 homers this season -- one shy of the 23 he hit last year.

"Am I refueled? I think everyone is pretty much refueled. It is always good to get some time off and clear your mind and come back and try to have a good second half," Kemp said.

Both homers came against Washington starter Tanner Roark, who had victimized the Padres with a shutout in 2014 and an 11-strikeout game later that season. He entered the game with a 1.73 ERA in four games against the Padres.

"He has good stuff ... good slider, good change," Kemp said of Roark. "Like I said he left a couple of them up in there in the zone. I don't think he meant to put them up there. I just put a good swing on them. We have had some battles over the years. I am just hitting the ball out of the ballpark more this year. I have never really tried to just hit home runs. Hopefully we can keep this going."

"This" is a streak of 20 games in a row with a homer -- the longest in the National League this season. "We are not worried about that. We are just trying to get Ws," Kemp said.

The fourth-place Padres (42-55) snapped a four-game losing streak while the first-place Nationals (57-40) lost for the fourth time in five games.

Luis Perdomo (4-4) gave up four hits while striking out three with one walk in seven innings in his ninth career start. He has allowed three runs or fewer in seven of his last eight starts and has yielded only 12 earned runs in his last five outings.

"I just followed my plan," he said through a translator. "At the end of the day, it's facing a major league lineup, whoever we're facing. I followed my plan, I kept my pitches low and I was able to use the sinker to get some outs."

Brad Hand entered to start the eighth for the Padres and gave up a one-out solo homer to Daniel Murphy, which cut the lead to 5-3. Brandon Maurer came on with two outs and retired Anthony Rendon on a flyout with a runner on base to end the frame before getting three outs in the ninth for the fourth save of his career.

Maurer retired Ben Revere for the final out with a runner on base.

The losing pitcher was Roark (9-6), who had his worst outing since allowing five runs in three innings on June 5 at Cincinnati. Wilson Ramos had three singles for the Nationals.

"He wasn't shard tonight, that's why we went and got him early. He made a couple of mistakes, leaving the ball up. It happens sometimes. Tanner's been lights out," manager Dusty Baker said of Roark. "Usually he keeps the ball down and away. Those balls were up and out over the plate. He just has to make better pitches."

Washington reliever Oliver Perez hit Brett Wallace with a pitch to lead off the ninth, which led home plate umpire Dan Bellino to warn both benches. Washington manager Dusty Baker then brought on closer Jonathan Papelbon, who got the last three outs after he had not thrown since Sunday.

The teams traded solo homers in the first inning.

Kemp connected with two outs off Roark to give the Padres a 1-0 lead. It was the first homer Roark allowed in 31 innings.

Washington's Jayson Werth responded with one out in the first to make it 1-1 on his 12th homer of the season. Werth extended his on-base streak to 26 games, the longest active run in the majors.

The Nationals were not done as Bryce Harper had a two-out single, stole second and scored on an RBI single by Ramos to make it 2-1.

The Padres got an RBI single in the fifth by Melvin Upton, Jr. and Kemp hit a three-run shot off Roark to build a 5-2 margin.

"Matt Kemp put us on his back and carried us," Green said. "That is what big-time players can do."

It was the second day in a row that an opponent hit two homers at Nationals Park. Justin Turner of the Dodgers went deep twice on Thursday against Stephen Strasburg.

Roark was pulled after giving up five runs on four hits in five innings. Felipe Rivero took over for Roark.

"I pride myself on going deep in the ballgames and giving my all for as long as I can. Everyone has nicks here and there, but just have to push through and keep getting better," Roark said.

Perdomo entered the game -- his first ever against Washington -- with a 7.36 ERA but allowed just four hits in the first five innings.

"He was great, especially when he gave up those run early," Green said. "After the home run he battles and gets out of the inning. He goes six more solid innings."

NOTES: The game time temperature was 90 degrees. ... The Padres signed Cuban outfielder Jorge Ona, 19, for a reported signing bonus of $7 million, according to MLB.com. "I was aware of the signing," manager Andy Green said. "It is a heck of a commitment from a financial perspective. Some of these (young) guys are going to end up stars. We hope Jorge is one of them." ... The Padres' pitching staff includes former Nationals RHP Edwin Jackson and LHP Matt Thornton. Jackson (1-1, 4.76 ERA) is slated to start Saturday against Washington RHP Max Scherzer (10-6, 2.94). ... San Diego LHP Ryan Buchter was drafted by the Nationals in the 33rd round in 2005 and made his big league debut in 2014 with the Atlanta Braves. ... San Diego RHP Paul Clemens went to Robinson High in Fairfax, Va., about 25 miles from Nationals Park. ... Washington 1B Ryan Zimmerman, who has been on the disabled list since July 8 with a left rib cage strain, began his minor league rehab assignment by going 2-for-4 on Thursday night for Class A Potomac in a 4-2 win over Winston-Salem.