WASHINGTON (AP) -- The Arizona Diamondbacks are hoping pitcher Trevor Cahill's problems are just a June swoon and not something more permanent.
The right-hander turned in another shaky performance Tuesday night and put the Diamondbacks in a hole they couldn't quite escape.
Adam LaRoche hit a three-run homer and Gio Gonzalez won for the first time since May 5 as the Nationals took a 6-0 lead and held on to defeat the Diamondbacks 7-5 Tuesday night.
Martin Prado homered and Paul Goldschmidt had three hits for Arizona. Diamondbacks second baseman Aaron Hill, playing his first game since going on the disabled list April 14 with a broken left hand, went 2 for 4 with a double, single and walk.
NL West-leading Arizona, which twice got within two runs, has lost two straight.
Cahill (3-9, 4.29), who left in the second inning of his last start after being struck by a line drive, lost his fifth straight. He allowed six earned runs on eight hits in five innings while walking two and striking out five.
"I don't know if he's trying to change his delivery or what. He changes from pitch to pitch," catcher Miguel Montero said. "Sometimes he pitches like (Brad) Ziegler, sometimes he's over the top, sometimes he's a little bit lower then, so it's hard.
"He's a guy that doesn't need to do too much. He just needs to grab the ball and just throw a good sinker down the middle and let it do the job."
Cahill hasn't completed six innings in any of his five June starts and his ERA in the month is 9.30.
"It's tough, because I'm going to keep doing what I'm doing and work on some things, but also try not to change too much," Cahill said.
Gonzalez (4-3) went 6 1-3 innings, giving up two runs on nine hits. He struck out four and walked one. Rafael Soriano allowed an RBI single to Miguel Montero in the ninth and had the tying runners on base, but picked up his 20th save.
"They stayed true to it and made it a good game down to the end," Diamondbacks manager Kirk Gibson said. "Had the go-ahead guy up, just wasn't enough. Got to play early in the game. You've got to pitch better."
Jayson Werth added a double, RBI single and two walks for Washington, which led 6-0 after five innings and snapped a two-game skid.
Washington matched its season high for runs in an inning with the five-run third off Cahill.
Kurt Suzuki walked, was sacrificed to second by Gonzalez, and scored on a single by Denard Span. Anthony Rendon singled and, after both runners moved up on a wild pitch, Werth singled to score Span.
LaRoche then fell behind Cahill 0-2, but hit a change-up into the bullpen in left-center for a three-run homer to make it 5-0.
"He walked the leadoff guy and he hung an 0-2 change-up to La Roche," Gibson said. "It just wasn't a very good inning for him."
Said Cahill: "For some reason I've noticed I've made a lot of those mistakes on my change-up. Just kind of leaving it up. I don't know if it's me trying to do too much with it or not, but I think the biggest thing is to just concentrate on the good one I throw and not try to overthrow it."
Washington added a run in the fifth when Ian Desmond's sacrifice fly scored Werth.
The Diamondbacks got on the board in the sixth when Hill doubled, went to third on a single by Goldschmidt and scored on Montero's single.
Goldschmidt's RBI single in the seventh off reliever Drew Storen scored A.J. Pollock to make it 6-2 and Hill then scored when Rendon couldn't field Montero's grounder.
Prado led off the eighth with a homer off Tyler Clippard to make it 6-4.
Washington added a run in the eighth when Steve Lombardozzi doubled and scored on an error by Ziegler.
NOTES: To make room for Hill, the Diamondbacks optioned left-hander Joe Paterson to Triple-A Reno. ... Arizona's Eric Hinske had his suspension for his role in the June 11 bench-clearing brawl with the Los Angeles Dodgers reduced from five games to one. He dropped his appeal and served the suspension Tuesday night. ... Arizona LHP Wade Miley (4-6, 4.70) opposes RHP Jordan Zimmermann (10-3, 2.26) on Wednesday.
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