The return of Daniel Murphy to Citi Field got the headlines this week. But for the Nationals, the three-game series against the Mets that concluded last night with a 9-1 Washington victory was about more than one former Met.

The Nationals were looking to set a much different tone than in 2015, when the Mets blew past them and left their division rivals in a shambles on the way to the World Series. Consider the tone-setting mission accomplished under new manager Dusty Baker.

First-place Washington delivered a solid thrashing to Matt Harvey to take two of three in the teams’ first meeting this season. Murphy hit a two-run homer in the first inning and the Nationals knocked out Harvey with a stunning seven-run third.

It’s was Murphy’s sixth home run of the season and the first he’s ever hit at Citi Field in which the Home Run Apple did not rise.

Even Bryce Harper, who had been 0-for-21 against Harvey after flying out to right in the first, contributed a single against the struggling righthander during Washington’s barrage of base hits in the third.

And Stephen Strasburg, who recently signed a seven-year, $175-million contract extension, allowed one run in six innings and struck out 10 to improve to 7-0 with a 2.80 ERA.

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Last season, the Mets went 11-8 against the Nationals, including the three-game sweep in Washington in September that pretty much sealed the NL East crown. The teams will meet again at Nationals Park on Monday for the first of a three-game rematch.

Murphy, who went 2-for-4 with a walk Thursday night and was 4-for-11 with four RBIs in the series, was booed as he came to the plate in the first. He launched a hanging 0-and-2 curve over the wall in right-center to give his new team a 2-0 lead.

In the third, the Nationals used six hits, a walk and an error by Asdrubal Cabrera to score seven runs and take a 9-1 lead against Harvey.

Ben Revere singled and moved to third one out later on Harper’s first hit off Harvey. Harper stole second, which led the Mets to intentionally walk Murphy to load the bases.

Ryan Zimmerman followed with a grounder to the shortstop hole that Cabrera bobbled for a run-scoring error. Anthony Rendon hit a two-run double off the glove of a leaping Michael Conforto in left to give Washington a 5-1 lead.

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There was more. Wilson Ramos singled in two more runs to make it 7-1. Danny Espinosa singled. Strasburg grounded to third to move the runners to second and third with two outs. They both scored to make it 9-1 as Revere hit a triple that eluded Yoenis Cespedes’ lunging try in center.

That was the end of the Dark Knight’s night. Harvey didn’t even wait for Terry Collins to reach the mound before handing him the ball and heading to the dugout.

The Nationals, who lead the third-place Mets by 2½ games, had made their early statement, both in the game and in the season.