PITTSBURGH -- The Washington Nationals are still figuring things out in the bullpen, but Tuesday night, the offense did more than enough to earn a victory.

The Nationals pounded Pittsburgh Pirates starter Chad Kuhl for 10 hits and six runs over four-plus innings on the way to an 8-4 series-opening victory at PNC Park.

The Nationals got to Kuhl (1-4) early and often, scoring in three of the first four frames.

Jayson Werth singled home Trea Turner in the first inning, then scored along with Stephen Strasburg on Ryan Zimmerman's two-run double in the third.

Werth finished 3-for-5, and Turner, Zimmerman and Bryce Harper each recorded two hits for Washington.

In the fourth inning, Wilmer Difo hit his first home run of the season, a two-run shot to left-center field.

Harper walked to lead off the fifth inning and scored on Matt Wieters' single. He also hit his 13th home run in the ninth.

Every Washington starter recorded a hit.

Kuhl was removed after facing two batters in the fifth inning. He had thrown 89 pitches. Pirates manager Clint Hurdle thought Kuhl may have been overthrowing at times.

"I think sometimes, he just gets involved in the game," Hurdle said. "I'm not so sure the added velocity helps. There was a time when his two-seamer and his change-up were playing at the same velocity. That's not a good indicator."

After the Nationals jumped out to a 6-1 lead, things got hairy in the seventh. Strasburg, who had allowed one run on three hits over his first six innings, left after facing two batters in the seventh.

Matt Albers and Oliver Perez each came into the game, but neither recorded an out as the Pirates scored three runs before Blake Treinen settled things down, recording three outs on two hitters with a double play and a strikeout.

Zimmerman had a throwing error on a potential double-play ball that could have ended the inning without any damage, but even with one of the runs being scored as unearned, the Nationals' bullpen now has a 5.35 ERA as a unit, second worst in the National League.

"We're still in the process trying to figure it out and get it together but in the meantime our offense is doing the job," said Nationals manager Dusty Baker.

After Treinen put out the fire in the seventh, Enny Romero threw a 1-2-3 eighth and Koda Glover struck out two while allowing two hits in the ninth. Baker said Glover has the chance to get more opportunities to pitch the ninth inning.

"We gave it to him tonight," Baker said. "We'll see. Usually he throws strikes and he throws quality strikes. He wants a shot at that so we've got to get his pitch count down so he can go the next day and the next day."

The Pirates struck early against Strasburg (4-1), with Josh Harrison hitting a solo home run in the first inning. The long ball was Harrison's sixth of the season.

Strasburg responded by allowing just one hit over the next five innings and he was charged with three runs on four hits. He struck out three and walked three in a 108-pitch outing.

The Pirates felt they had a good approach against Strasburg, with four extra-base hits, but couldn't get hits to fall at critical times. They were 2 for 11 with runners in scoring position.

"You can't get too upset by it because the process is there and you're still squaring up the baseball," said first baseman Josh Bell, who was 1 for 4. "If they're not falling for you at the time, you can't change too much. The game gets tough at times, but you just turn the page."

Harrison and Adam Frazier collected two hits apiece for Pittsburgh.

Daniel Hudson, Johnny Barbato and Wade LeBlanc combined to pitch five innings of relief for the Pirates. The only blemish was a two-run home run by Harper in the ninth, given up by LeBlanc.

NOTES: Pirates RF Gregory Polanco did not play after leaving Sunday's game in Arizona with a sore left hamstring. ... Pittsburgh RHP Felipe Rivero (sore neck) did not pitch. He hasn't pitched since May 13. ... RHP Daniel Hudson finished the fifth inning for the Pirates. He has typically pitched the eighth inning this season, but he had given up nine runs in his last six innings. He allowed an inherited runner to score and gave up one hit. ... Pirates CF Andrew McCutchen went 0-for-4 with a strikeout, including an 0-for-2 mark with runners in scoring position. His batting average is a career-low .206. ... Nationals 1B Ryan Zimmerman's two RBIs increased his major-league-leading total to 38. He also leads the league with a .388 batting average. ... Washington RF Bryce Harper hit a two-run home run, his 13th of the season. PNC Park had been the last National League ballpark in which Harper had not homered.