PHOENIX -- Bryce Harper homered and drove in two runs, Tanner Roark struck out a season-high 11 and Sean Doolittle stranded the potential tying run to preserve the Washington Nationals' 4-3 win over the Arizona Diamondbacks on Saturday night.
Roark (8-6) gave up two runs and three hits in seven innings for the NL East-leading Nationals.
Harper hit his 25th home run of the season on a full-count changeup from Anthony Banda (0-1), who lost in his major league debut.
Chris Iannetta hit a two-out RBI double in the bottom half, but the Nationals opened a 4-1 lead with a three-run sixth.
Harper hit an a run-scoring double and scored on Ryan Zimmerman's double, and Anthony Rendon beat out an RBI single that sent Zimmerman home.
A.J. Pollock tripled in the bottom half and scored on Jake Lamb's groundout, and Arizona reliever Jorge De La Rosa got out of bases-loaded trouble in the seventh when he struck out Harper and Zimmerman.
Doolittle, acquired from Oakland last weekend, walked Lamb leading off the ninth. Iannetta hit a grounder to third, and Rendon's throw to second went into right field for an error that put runners on the corners.
Paul Goldschmidt hit a sacrifice fly, Chris Owings flied out and Doolittle struck out Ketel Marte for his second save with the Nationals.
Banda allowed four runs and seven hits in 5 2/3 innings, struck out five and walked none.
Brian Goodwin, who had three hits, was thrown out at third base trying to stretch a third-inning double, with right fielder David Peralta throwing to second baseman Chris Owings, who made the relay.
GOLDY'S 'DAY OFF'
Manager Torey Lovullo gave Goldschmidt a day off from the starting lineup, but the All-Star pinch hit in the ninth. "He went to the All-Star Game and didn't get the the four days off that everybody else had," Lovullo said. "He always wants to be in there. It was one of those decisions that I had to make where I said take the day off and be ready for a Sunday day game."
Diamondbacks OF J.D. Martinez remains day to day with a bruised hand, which is feeling better, Lovullo said.
Nationals: RHP Stephen Strasburg (10-3) faces Arizona on Sunday. He is coming off a four-hit, 11-strikeout performance in a win over Cincinnati.
Diamondbacks: LHP Robbie Ray (9-4) faces the team that originally drafted him in 2010. Ray is 0-3 with a 6.48 ERA in three starts against Washington.