WASHINGTON (AP) Nationals rookie right-hander Joe Ross delivered yet another strong performance in beating Arizona 8-3 on Thursday.

Ross learned after the game he was staying in Washington's rotation replacing veteran Doug Fister, who's going to the bullpen.

''I'm going to take the role and try to help the team,'' the 22-year-old Ross said after allowing a run and five hits while striking out seven in six innings. ''I wanted to go out there and do my best and hopefully make them make a (tough) decision.''

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Manager Matt Williams said that Ross (3-3) deserves to keep starting ahead of the struggling 31-year-old Fister (4-7), who has started in all but three of his 170 career games. Fister, whose contract expires after the season, was unavailable for comment.

''It's a difficult task when you've been a starter for so long, but (Doug's) willing to do whatever he can to help us win,'' Williams said

The Nationals had to make a choice with Stephen Strasburg returning from the disabled list Saturday.

Ross certainly delivered for the Nats, who had lost four of five, as they closed with 1 1/2 games of the idle front-running New York Mets in the NL East.

''He threw all his pitches well for strikes when he needed to, worked quickly, and continues to pitch well,'' Williams said of Ross, who was first recalled from Double-A Harrisburg on June 6. ''The changeup is key for him and the breaking ball is key for him. He hit the outside corner, didn't give `em much to pull. He was in command.''

Ian Desmond, the National League's Silver Slugger shortstop the past three years, was scuffling so badly at the plate that he was rested on Wednesday night.

The day off paid off as Desmond sent the first pitch he saw from Arizona right hander Jeremy Hellickson (7-8) in the second inning into the Washington bullpen for his 12th home run, ending a 2-for-35 skid. Desmond's double to left leading off the fourth gave him more extra base hits than he had produced in his previous nine games. He moved to third on Wilson Ramos' single and scored on Michael Taylor's fielder's choice.

Jarrod Saltalamacchia, who was batting just .170, led off the Arizona fifth with his third homer to narrow the margin to 2-1.

Ramos singled home Bryce Harper (on base all five times) and Werth with two outs in the fifth, chasing Hellickson and making it 4-1.

''Just working way too hard out there right now,'' Hellickson said. ''I felt like the bases were loaded every inning. You can't rely on making a big pitch every inning to get out of it. Just got to have some easy outs and easy innings.''

Arizona loaded the bases against Casey Janssen in the seventh. Second baseman Anthony Rendon raced into short center to rob Chris Owings, but Ender Inciarte doubled home two runs before Matt Thornton got out of the inning. Pinch-hitter Ryan Zimmerman doubled home Taylor in the seventh before Clint Robinson put the game away with his fifth homer, a three-run shot, in the eighth.

Despite the defeat, the Diamondbacks felt good about their 6-4 road trip.

''We would love to come away with winning the series, but . it feels like this team just keeps getting a little bit better as we go on and it will be fun to see how we finish,'' said second baseman Aaron Hill.

TREINEN'S BACK

The Nats recalled Blake Treinen from Triple-A Syracuse and sent fellow right handed reliever Aaron Barrett to the Chiefs. Treinen, who was demoted after surrendering four runs and five hits in just 1/3 of an inning against the Los Angeles Dodgers on July 19, allowed no runs and six hits over 12 innings in five games for Syracuse. Treinen pitched a scoreless ninth on Thursday.

GOLDSCHMIDT SITS

Diamondbacks All-Star first baseman Paul Goldschmidt didn't start on Thursday for the first time since May 21. He broke a 0-for-15 slump with three hits on Wednesday. Saltalamacchia started at first for the first time since 2012.

TRAINER'S ROOM

Diamondbacks : RHP Chase Anderson (triceps) will be activated from the DL in time to make tomorrow's start against visiting Cincinnati.

Nationals: RHP Strasburg (oblique) will be activated from the disabled list to make Saturday's start against visiting Colorado.

UP NEXT

Diamondbacks: Anderson (4-4, 4.37) makes his first start since going on the disabled list on July 19 with an inflamed right triceps. Anderson pitched four scoreless innings in his lone rehab start.

Nationals: RHP Jordan Zimmermann (8-7, 3.54) allowed five runs and six hits in six innings in his last start. He's 0-2, 5.08 in four starts since the All-Star break.