PHOENIX (AP) -- The Arizona Diamondbacks battled Washington Nationals ace Stephen Strasburg into several hitters' counts Friday night and it still didn't help.
Strasburg allowed one hit over six innings and Ryan Zimmerman homered to help the Nationals rout the slumping Diamondbacks 9-1 for their seventh straight win.
"He has good stuff obviously," Diamondbacks manager Kirk Gibson said. "You all see his velocity. I actually thought we had a good approach against him and got five three-ball counts the first time in the order. He has good stuff and you've got to play a lot better to beat that."
Arizona starter Trevor Cahill (9-10) was in trouble early. He put two runners on in the second, escaping without allowing a run, but surrendered a triple to Steve Lombardozzi and a sacrifice fly to Bryce Harper as the Nationals took a 1-0 lead in the third.
Chris Johnson tied the game 1-1 in the fourth with a run-scoring single, his 17th RBI in 11 games, but Cahill surrendered home runs to Zimmerman and Michael Morse in the fifth and sixth innings as Washington took control.
Cahill (9-10) went six innings, allowing four runs, six hits and three walks while striking out four.
"They made me work and it was one of those nights I couldn't put anyone away," Cahill said.
The Diamondbacks lost for the fifth time in seven games but remained four games behind the San Francisco Giants in the NL West. San Francisco lost 3-0 to Colorado on Friday.
Strasburg (13-5) had been dealing with slight soreness in his mid-back from sleeping awkwardly a couple of starts ago. The stiffness was exacerbated Friday when the game was delayed for nine minutes when Miguel Montero fouled a pitch off home plate umpire Dale Scott's mask, forcing the crew chief from the game.
Strasburg pitched into trouble for the first time all game, walking Montero after already having walked Justin Upton before allowing Johnson's single.
Johnson is 3 for 6 with three RBIs in his career against the Nationals' ace.
"You're not consistently going to do well against him," Johnson said. "If you get that chance you're going to have to jump on him and we didn't have that chance."
Strasburg struck out six, walked four and threw 58 of his 104 pitches for strikes en route to his second career one-hit outing.
Strasburg raised his season innings total to 133 1-3, just under 27 fewer than the 160-inning cap the Nationals have planned for him in his first full season back from Tommy John surgery.
Lombardozzi had a career-high four hits and scored three runs and Harper added two sacrifice flies for the Nationals, who remained 4 1-2 games ahead of Atlanta in the NL East.
Morse led off the sixth with his homer, a 446-foot shot onto the concourse above the wall in center field.
"The two homers hurt us," Gibson said. "We just didn't have a lot of energy to overcome that tonight."
Lombardozzi singled in the seventh and scored on a throwing error for his third run of the game.
Washington added four runs in the ninth off Mike Zagurski, the Diamondbacks' fourth pitcher, the last two coming on a double by Jayson Werth down the left-field line.
NOTES: Johnson said Harper will get Saturday off and return for the series finale Sunday. . Johnson has 17 RBIs in 11 games with Arizona. . Strasburg's four walks were his most since a four-walk, three-inning start June 30 at Atlanta. ... Montero's fourth-inning at-bat was an adventure. One pitch before fouling the ball off Scott's mask, he lost his grip on his bat and it flew into the stands, striking a fan in her abdomen. She was OK and later returned the bat. . Scott immediately spun and dropped to a knee after he was hit before slowly leaving the field under his own power. C.B. Bucknor came in from third base to replace Scott. ... Johnson is 3 for 5 with three RBIs in his career against Strasburg. ... Morse's home run extended his suddenly shortened hitting streak to eight games. Morse had an 18-game streak before a scoring change made Friday afternoon turned his lone hit Aug. 2 to an error. ... Before the game, the Diamondbacks placed RHP Josh Collmenter on the 15-day DL because of ulcers and recalled RHP Brad Bergesen from Triple-A Reno. Collmenter is 3-3 with a 4.24 ERA in 22 games, including nine starts.