WASHINGTON (AP) -- Bryce Harper and Adam LaRoche each drove in two runs, leading the Washington Nationals over the Pittsburgh Pirates 5-4 Friday night for their fourth straight win.
Denard Span added three hits as the NL-East leading Nationals opened a 10-game homestand.
Tanner Roark (12-7) gave up three runs on five hits over 5 2-3 innings. He struck out four and walked two.
Rafael Soriano allowed three hits in the ninth, including Pedro Alvarez's RBI single, but held on for his 29th save.
Starling Marte hit a two-run homer and singled for the Pirates, who have lost three straight.
Charlie Morton (5-12) lasted just three innings in his shortest start of the season, allowing five runs on seven hits and three walks.
The first five Nationals hitters of the game reached base. Morton caught a break when Span was thrown out trying to steal third, but LaRoche's single made it 1-0.
With bases loaded, Harper fouled a 2-2 pitch off his right foot and needed a several moments to recover. He stepped in and eventually lined a 3-2 pitch to right-center field for a two-run single, making it 3-0.
Harper finished with two hits. Off to a slower-than-usual start this year, he homered twice this week during a three-game sweep of the Mets in New York.
LaRoche and Wilson Ramos singled home runs in the third to make it 5-0.
The Pirates got to Roark in the fourth. Neil Walker doubled and Marte connected for his sixth homer. Alvarez then doubled home a run with two outs to pull Pittsburgh within 5-3.
Pirates: RHP Stolmy Pimentel (right ankle sprain) was placed on the 15-day disabled list. ... SS Jordy Mercer, who left Thursday's game with right forearm tightness, wasn't in the lineup. Mercer, who had started 49 straight games, grounded out as a pinch-hitter. ... Walker, who had missed 11 of the last 12 games with back tightness, started and went 1 for 4.
Nationals: RF Jayson Werth (right shoulder) missed his fourth straight game. Manager Matt Williams said Werth was available to pinch-hit and could return to the lineup Saturday, or more likely Sunday. OF Nate McLouth (right shoulder inflammation) is going to get a second opinion on his ailing shoulder. "It's not responding as well as he'd like it to respond," Williams said.
Pirates: LHP Jeff Locke (4-3, 3.98) makes his second career start against the Nationals. He allowed three earned runs in five innings of a no-decision on May 4, 2013, at PNC Park.
Nationals: LHP Gio Gonzalez (6-9, 4.00) is 2-0 with a 3.28 ERA in four career starts against the Pirates. His teams (Nationals 3-0, A's 1-0) are undefeated in those games.