The Nationals became the last team in the majors to post a three-game winning streak by scoring a 9-6 victory over the Marlins on Sunday. (Katherine Frey/The Washington Post)

For the vocal contingent of Washington Nationals fans who dismissed their team’s previous two wins because they came against the Miami Marlins, a team once stuffed with future stars but since stripped to the studs, Sunday’s 9-6 victory at Nationals Park offered a counterargument.

The biggest point — bigger than starter Erick Fedde’s five scoreless innings, bigger than the Nationals playing one of their best defensive games of the season, bigger than anything else — was whom they did it against. The Nationals battered the Marlins’ de facto ace, Caleb Smith, who entered the game with the fourth-best ERA (2.38) in the majors. The left-hander had compiled his strong start by navigating some of baseball’s tougher lineups while not once in nine starts allowing more than three runs.

That point narrowly survived a near-supernova by Nationals relievers, who turned a 9-0 lead heading into the eighth into a 9-6 edge in the ninth. Yet the offense Sunday did what starter Patrick Corbin had done in his shutout Saturday: It saved the team from asking too much of the bullpen. With the victory, Washington became the last team in the majors to string together a three-game winning streak and trimmed its deficit in the National League East to nine games. The key to it all was knocking Smith out after three innings and five runs, boosting his ERA to 3.05.

“Get him out over the plate and get him up,” Nationals Manager Dave Martinez said of how his offense beat Smith. “That’s what we talked about, and we were able to do that. We laid off some pretty good pitches down in the zone, and we were able to get him up a little bit.”

In the third, the Nationals’ offense looked every bit as dangerous as it had promised to be in spring training — just moments after the Nationals were poised to look every bit as futile as they had been in the season’s first month and a half. After two quick outs, Adam Eaton doubled and Anthony Rendon took an intentional walk, but Smith jumped ahead of Juan Soto 1-2. The Soto of two weeks ago might have struck out, might have killed the rally before it began. But the 20-year-old is now scorching at the plate in large part because he has shown the patience his manager has preached.

Soto laid off three straight pitches, including a fastball inches low, and worked a walk to load the bases. A single by Howie Kendrick and a double by Brian Dozier brought home four runs, extending a lead Kendrick built in the second with a leadoff solo homer.

“There’s a reason why he’s been playing for so long,” Rendon said of Kendrick, a 14-year veteran. “That man is a bulldog.”

The Nationals’ 35-year-old utility infielder, whose positional flexibility and unexpected reliability were invaluable amid the patchwork lineups of late April and early May, continued to be a lifeblood of the offense despite his gradual return to a reserve role. Kendrick finished 3 for 5 with three RBI, serving as the primary architect of a lead that ballooned and was insurmountable by the Marlins’ major league-worst offense. The Marlins roughed up reliever James Bourque for four runs in the ninth in his major league debut, but it was too late.

Miami briefly had Fedde on the ropes — the reliever is still stretching himself back into starter shape — but didn’t take advantage. Fedde worked with purpose early, throwing a pitch every 15 seconds or so and showing his sinker, cutter, change-up and what he calls a “slurvey curve.”

In the third, Fedde got into a jam with his curveball — which was mostly effective but, just then, had been smacked down the first base line by Harold Ramirez for a double — and he got out of it with one, too. After Fedde intentionally walked Brian Anderson to load the bases, Neil Walker waved helplessly at a low curve as the Nationals right-hander wriggled free. Fedde pumped his fist.

“Those are the moments you find out who you are,” he said. “It’s fun.”

Still, after throwing 21 of his first 29 pitches for strikes, Fedde had managed to find the zone on just 13 of 27 pitches in that inning. The next inning, instead of showing patience to find out whether a fatigued Fedde might wander into a mistake or two, the Marlins hacked. All three Miami hitters flied out to center, two on 1-0 counts, and Fedde escaped having thrown eight pitches, setting himself up to get through the fifth, too.

After the game, Fedde was asked whether he felt he had made a compelling case to remain in the rotation once Aníbal Sánchez and Jeremy Hellickson return from the injured list. “Definitely,” he said. “My job here is to make it as tough for them to send me down. Whether they want me in the rotation or the ’pen, I’m happy just to help this team get some wins.”

By the time the Marlins finally had gotten into the Nationals’ bullpen, the game seemed too far gone. The Nationals led 5-0, and after a 24-minute delay brought on by sudden, torrential rain, the offense did not slow in the sixth. Michael A. Taylor doubled in a run. Rendon tripled in two more. Soto’s sacrifice fly scored another.

The Marlins broke the seal in the eighth with a two-run homer by Walker, but his big hit arrived five innings too late. The Nationals limited the damage, and Wander Suero left the tying run in the on-deck circle with a strikeout of Starlin Castro to end it. After the game, Dozier brushed aside the unease of how the game ended and zeroed in on the outcome.

“It’s good knowing that we can string together some wins to get the confidence back in here and know that we’re a really good ballclub,” he said. “It started with this series, and hopefully we can keep it going.”