New York, off to a 4-1 start, will be Washington's guest for a weekend series that begins Thursday afternoon with the Nationals' home opener.
"It's crucial. It's going to set the pace for the rest of the season with those guys," Mets pitcher Noah Syndergaard told mlb.com. "They're our rivals. They're the front-runners. It's always nice to go out there and give them a little bit of a challenge. It's going to be very crucial for us to go out there and attack them."
Washington (4-2) won the NL East by 20 games a year ago. New York finished 27 back.
On Wednesday, the Mets closed their season-opening homestand with a 4-2 win over the Philadelphia Phillies. Syndergaard lasted just four innings, but New York's bullpen threw five scoreless frames and Amed Rosario's two-run triple in the sixth broke a 2-2 tie.
"Obviously, he's come up big so far this season with some two-out RBIs," Mets manager Mickey Callaway told mlb.com regarding Rosario, who is batting .333 with five RBIs in five games. "And another big one tonight."
New York relievers faced the minimum 15 batters over the final five innings and lowered the bullpen ERA to 1.33.
Yoenis Cespedes' second homer of the season -- a two-run shot in the first -- gave the Mets an early lead.
New York will send right-hander Jacob deGrom (1-0, 1.59 ERA) to the mound against Stephen Strasburg (1-0, 1.42 ERA).
Left-handed hitting outfielder Michael Conforto, who underwent left shoulder surgery in September, is expected to come off the disabled list and make his 2018 debut against the righty Strasburg.
The Nationals burst out of the gate with four wins, but on Wednesday they dropped their second straight 7-1 in Atlanta.
Washington didn't hit or field well behind Max Scherzer (1-1), who allowed five runs -- two earned -- on six hits over five innings.
"I didn't have good put-away pitches. I got to two strikes, and just didn't seem to put guys away. That led to at-bats kind of getting extended," Scherzer told the Washington Post. "They were able to grind out their at-bats, and get hits on pitches that later in the at-bat I didn't execute as well."
Bryce Harper went 0-for-3 and struck out for the first time this season, and the Nationals managed just six hits of Mike Foltynewicz and five Atlanta relievers.
Wilmer Difo booted a routine grounder with two outs in the first inning that put two men on for Preston Tucker, who homered off Scherzer to make it 3-0.
"It was just a regular ground ball," Difo told the Post via an interpreter. "I tried to field it and make the play, and unfortunately it didn't come out that way."
Washington won the 2017 season series against New York 13-6, including a 23-5 home rout on April 30. Syndergaard started that game but left in the second injury with the lat injury that essentially ended his season.
In 12 career starts against the Nationals, deGrom is 5-4 with a 2.77 ERA.
Bryce Harper is 9-for-24 with a homer run and five walks in his career against deGrom, while Trea Turner is 5-for-15 and Ryan Zimmerman is 5-for-16 (.313) with two homers. On the flip side, Anthony Rendon is 0-for-19 and Michael A. Taylor is 1-for-19 versus deGrom.
Former Met-turned-Met-killer Daniel Murphy (.386, nine homers, 35 RBIs against New York) is out as he recovers from microfracture surgery on his right knee.
Strasburg is 8-4 versus New York with a 2.64 ERA.