WASHINGTON — Max Scherzer caused spasms Sunday instead of getting them, a step in the right direction for the Mets in attempting to rejuvenate their rotation.

The Mets celebrated Scherzer’s revival with a breakout game — or, more succinctly, inning — at the plate in an 8-2 victory over the Nationals in the second game of a doubleheader.

Earlier in the day, the teams resumed a suspended game from Saturday. The Mets scuffled with runners on base in a 3-2 loss.

Scherzer’s performance was of significant interest, after he was scratched from his Tuesday start with neck spasms — and he previously told The Post he was fighting to stay off the injured list because of discomfort near his scapula.

Over five innings on this day, he allowed one earned run on two hits and two walks with six strikeouts.

He departed after 83 pitches with the Mets already in control with a seven-run lead in the sixth inning.

Also telling was Scherzer saw an increase in velocity, with his four-seam fastball averaging 94 mph.

He had experienced a dip in his previous start in Detroit, where he returned from a 10-game suspension for violating MLB’s rules on foreign substances and allowed six earned runs over 3 ¹/₃ innings.

This latest homecoming, to Nationals Park — Scherzer won two Cy Young awards pitching for Washington and one for Detroit — went much smoother.

Scherzer allowed a run on CJ Abrams’ double in the second inning, but otherwise avoided trouble. His solid outing came four days after Justin Verlander stifled the Reds with one earned run over seven innings, giving the Mets their first real glimpse of what the top of this rotation can be.

The Mets broke it open in the fifth inning, when they sent 12 batters to the plate and scored eight runs — or one more than they had totaled in their previous four games combined.

Instead of relying on the big hit, the Mets simply kept the line moving.

Starling Marte and Mark Canha each had two hits in the inning and Francisco Lindor’s dribbler that brought in a run with two outs was also instrumental, after Brandon Nimmo’s RBI single.

Tommy Pham and Brett Baty each reached base in the inning with a walk and Pete Alonso was hit by a pitch.

After waiting nearly four hours in a weather delay the previous night before the game was suspended, the teams completed their missing seven innings earlier on Sunday.

The suspended game resumed with the Nationals ahead 1-0 and the Mets with runners on second and third base with one out in the top of the third.

One pitch later the game was tied: Brandon Nimmo hit a sacrifice fly. Before the suspension, Michael Perez’s double had sent Daniel Vogelbach to third base.

Vogelbach scored the Mets’ first run.

The Mets loaded the bases in the fourth inning on singles by Alonso, Baty and Marte, but Vogelbach struck out and Luis Guillorme was retired to end the threat.

“It’s tough right now,” Vogelbach said. “My whole goal with the bases loaded is to put the ball in play … I chased and couldn’t get them in.”

Joey Lucchesi (who was optioned to Triple-A Syracuse before the game resumed) allowed a run in the first inning on Joey Meneses’ RBI single.

Abrams’ RBI single against Stephen Nogosek in the fourth gave the Nationals a 2-1 lead.

Jeimer Candelario walked with two outs and Stone Garrett was plunked by a pitch before Abrams delivered.

Perez singled in the seventh — the catcher’s third hit of the game — and scored the tying run on Jeff McNeil’s sacrifice fly following Nimmo’s double.

Abrams put the Nationals ahead 3-2 in the bottom of the inning on a leadoff homer against Dominic Leone.

McNeil came to the plate with the tying run at second base in the ninth, but was retired by Kyle Finnegan on a long fly to center that ended the game.