WASHINGTON (AP) -- Pittsburgh Pirates starter Charlie Morton wished he could explain this miserable three-inning effort.
His manager said it might not be possible.
Morton allowed all five runs in his shortest outing of the season and the Pirates fell 5-4 to the Washington Nationals on Friday night.
"We didn't see a lot of consistency of sink and sharpness to the breaking ball, the misfires sometimes even in the zone," said Pirates manager Clint Hurdle. "Just got behind and wasn't able to recover."
Morton (5-12) allowed seven hits and walked three before exiting for a pinch hitter in the fourth. He gave up three runs in the first.
Five days ago, he yielded four runs in the fifth inning of an 8-2 loss to San Diego, and has allowed three runs or more in 13 innings this season.
"I just, I don't know," Morton said, trying to explain the first inning. "I mean, you saw what happened."
Bryce Harper and Adam LaRoche each drove in two runs to help the NL East-leading Nationals stretch their win streak to four games.
Denard Span added three hits and Tanner Roark (12-7) gave up three runs on five hits, including a two-run homer to Starling Marte, over 5 2-3 innings.
The Pirates scored another run off Nationals closer Rafael Soriano in the ninth, who escaped with his 29th save when Josh Harrison popped to the catcher with runners on the corners.
"We pushed about as far as we could to get one more swing, one more pitch," said Hurdle, whose club has lost three straight.
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.
"I didn't feel like they were driving balls off of me," Morton said. "I was falling behind."
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.
The Pirates activated RHP John Axford, who was claimed off waivers from the Cleveland Indians on Thursday, reuniting him with fellow Ontario, Canada native Russell Martin. The pair played together for Team Canada when they were 18.
"I put a lot of faith and trust in Russ, not only just because he's Canadian, but he's a great catcher as well," Axford quipped before Friday's game.
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.
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