Jackson hadn't won a game in nearly eight weeks, and LaRoche was in an 0-for-13 rut. Both came through in a 5-3 victory on Wednesday night. Jackson pitched seven effective innings, and LaRoche hit a three-run homer to fuel Washington's second successive victory against the Mets.
Jackson (2-3) allowed three runs, two earned, and three hits to earn his first victory since April 14 against Cincinnati. The right-hander was 0-3 with a 3.33 ERA in his previous eight starts.
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"It's been like a while," Jackson said.
Sean Burnett pitched a perfect eighth inning, and Tyler Clippard worked the ninth for his fifth save in six chances to complete the three-hitter.
Jackson didn't complain about his team's lack of run support, but LaRoche's first-inning home run set the tone.
"They're not going out and not scoring on purpose," Jackson said.
Before LaRoche's home run, Nationals manager Davey Johnson told his coaches that he expected a big hit from the first baseman.
"He's been quiet for a long time. He's going to start getting hot," Johnson said.
LaRoche added a fourth RBI on a sacrifice fly in the seventh.
Johnson got Michael Morse back on Saturday after the right fielder missed the first two months of the season with a back strain. Morse had two hits and an RBI, and is 4 for 8 in his last two games.
"The first two guys get in -- then, thunder's coming," Johnson said.
LaRoche thought his recent at-bats were poor, but now he is pleased to be part of the middle of the order with Ryan Zimmerman ahead of him, and Morse behind him.
"This is kind of what we were talking about in spring training. This is what we're capable of doing, kind of getting everybody going at once," LaRoche said.
Jordan Zimmermann and Jackson, Washington's third and fourth starters, haven't been as fortunate as Stephen Strasburg and Gio Gonzalez, the top two. Zimmermann and Jackson have a combined record of 5-8. Strasburg and Gonzalez are 13-3.
"When you're pitching behind those guys, you're always going to hear about what they're doing," Morse said.
"He's been as sharp as any of them," Johnson said of Jackson. "He was exceptional. Just what we needed."
Lucas Duda drove in a run and walked twice for New York, which has lost three straight. David Wright, Ike Davis and Kirk Nieuwenhuis had the Mets' only hits.
"They don't lead the National League in pitching without having some guys get you out," New York manager Terry Collins said.
LaRoche got the first-place Nationals off to a fast start, belting his ninth home run of the season in the first inning against Jeremy Hefner (1-3). Bryce Harper reached on an error by second baseman Daniel Murphy, and Ryan Zimmerman walked before LaRoche hit a drive into the right-field bullpen.
"I wish I could get that pitch back," Hefner said. "It hung for him practically on a tee. He did what he's supposed to do with that pitch."
The Mets got on the board in the third. Omar Quintanilla reached on a leadoff walk, advanced on Hefner's sacrifice and scored on Nieuwenhuis' single.
Wright singled and scored on Duda's groundout in the fourth, and Quintanilla had a run-scoring bouncer in the seventh but that was it against Jackson, who struck out six and walked four.
Hefner allowed four runs, three earned, and seven hits in six innings.
The Mets activated OF Jason Bay from the 15-day disabled list. Bay had been sidelined with a fractured rib since April 23. He didn't play, but Collins said Bay would be in the lineup on Thursday afternoon. ... RHP Chris Young, who started on Tuesday for the first time in more than a year, went on the paternity list. RHP Pedro Beato was reinstated from the DL. He hadn't pitched this year because of shoulder stiffness. INF Josh Satin was designated for assignment. ... Mets INF Ruben Tejada, on the disabled list with a strained right quad, is back in New York for an exam, one day after he took himself out of a minor league game when the quad tightened up. ... Johnson said C Carlos Maldonado would go on the DL with a back injury, and the team would recall OF Tyler Moore from Triple-A Syracuse. ... Johnson said Morse, who played his fourth game after returning from a strained back muscle, likely would DH when the team plays at Boston on Friday. ... The Mets are scheduled to send RHP R.A. Dickey (8-1, 2.69 ERA) to the mound against Washington RHP Chien-Ming Wang (1-1, 6.43) on Thursday.