PHOENIX -- Dusty Baker is getting to know his new relief pitchers. And he's thrilled to do so.

Baker's recent acquisitions from Oakland, Sean Doolittle and Ryan Madson, allowed the Washington Nationals to hang on for dear life amid a raucous atmosphere in the final two innings in their 4-3 win over the Arizona Diamondbacks on Saturday night.

After starter Tanner Roark (8-6) limited the Diamondbacks to two runs in seven innings, Madson pitched a scoreless eighth and Doolittle allowed one unearned run in the ninth to preserve a big win for a bullpen that has been unreliable in recent years.

"Madson has been great for us," said Nationals outfielder Bryce Harper, who homered and doubled. "And Doolittle never panics.

"It's great to see. It's a lot of fun to have a back end like that, possibly, hopefully, we get one more guy in that pen."

Baker said he received some advice on how to use the pair from Athletics manager Bob Melvin, who also told him the Nationals were getting two of our best citizens and two of our best players.

"It's a great compliment when you get that from a manager," Baker said.

The Diamondbacks, down 4-2, threatened to pull the game out in the bottom of the ninth inning.

Jake Lamb led off by drawing a walk from closer Sean Doolittle. Third baseman Anthony Rendon, trying for a force play at second, made a throwing error on Chris Iannetta's ground ball, putting runners at first and third with nobody out.

With the crowd roaring as though the teams were in the postseason, pinch-hitter Paul Goldschmidt's sacrifice fly to right drove in Lamb to make it 4-3.

"What can happen in those situations is the game can really speed up on you," Doolittle said. "Once you start getting guys on base, the crowd, the energy of the stadium can kind of take over. It speeds everything up.

"You have to be mindful, you have to step off the mound and slow the game down a little bit, kind of press reset, and go back through maybe the advance report, remind yourself of what you've got to do."

Baker put it more succinctly: "Doolittle has guts. He came right after Goldy. Not many players go after him like that."

Doolittle then got Chris Owings on a deep fly to right field for the second out and struck out Ketel Marte to end the game.

"A great atmosphere, a great night, just unfortunately came up on the wrong end of things," Arizona manager Torey Lovullo said. "It is such a letdown, an emotional letdown when it happens the way it does, when the crowd is behind you."

Roark, in his second straight strong outing, gave up three hits while striking out 11 and walking one.

The major league debut for Arizona's Anthony Banda began well as he gave up only Bryce Harper's 25th homer of the season in the first during his first five innings. But when Lovullo elected to have Banda try to pitch through Washington's potent batting order for a third time, the Nationals pounced.

With one out in the sixth, the Nationals broke a 1-1 tie when Chris Heisey tripled and Harper doubled him home. Ryan Zimmerman followed with a double to center to score Harper for a 3-1 lead.

With two outs, Rendon barely beat Lamb's one-hop throw to first from behind third base to score Zimmerman and make it 4-1.

Banda gave up four runs and seven hits in 5 2/3 innings. He struck out five and did not walk a batter. He was optioned back to Triple-A Reno after the game.

The Diamondbacks cut the lead to 4-2 in the sixth when A.J. Pollock tripled and scored on an infield groundout by Lamb.

Harper hit his 25th homer, a solo shot deep into the right-field pavilion in the first inning. The homer extended Harper's hitting streak to 15 games, the longest active run in the majors.

The Diamondbacks tied the score in the bottom of the first when Iannetta doubled to the left-field corner to drive in Pollock (2-for-4), who singled.

NOTES: Nationals manager Dusty Baker said OF Chris Heisey suffered a groin injury, which he fears will further deplete his thin outfield group. ... Diamondbacks 1B Paul Goldschmidt was not in the starting lineup on orders from manager Torey Lovullo. "I feel like it was the right thing, well timed for him," Lovullo said. "He went to the All-Star Game. He didn't have the four days that everybody else had off." Goldschmidt hit a sacrifice fly as a pinch hitter in the ninth inning. ... Nationals OF Ryan Raburn will go on bereavement leave Sunday because of the death of his grandfather. He pinch hit in the ninth inning of Saturday' night's game, grounding out. ... This series features nine National League All-Stars: Nationals OF Bryce Harper, 2B Daniel Murphy, RHP Max Scherzer, RPH Stephen Strasburg and 1B Ryan Zimmerman; and D-Backs' 1B Paul Goldschmidt, RHP Zack Greinke, 3B Jake Lamb and LHP Robbie Ray.