WASHINGTON — This is the vaunted pitching on which the Mets’ 2019 fortunes rest?

Only hours after assistant general manager John Ricco stood pat with his best pitchers at the non-waiver trade deadline, expressing a desire to contend next season with a strong rotation, Steven Matz orchestrated an abomination against the Nationals that screamed “sell, sell, sell.”

In a historic implosion, the Mets lost 25-4 at Nationals Park.

The demolition — which included Jose Reyes entering in the eighth inning for his first career pitching appearance — was the worst loss in Mets history. It topped the Mets’ 26-7 loss to the Phillies on June 11, 1985 at Veterans Stadium.

“It’s a tough loss,” manager Mickey Callaway said. “It’s embarrassing. We have got to do better than that.”

Reyes allowed homers to Matt Adams and Mark Reynolds in the eighth inning, as the Nationals scored six runs to ensure the worst loss in Mets history. Ryan Zimmerman added levity to the situation, by faking as if he might charge the mound after getting hit by a floating Reyes pitch.

“Any time you lose a game and you allow 25 runs and you lose 25-[4], you have to feel disappointed about it,” Reyes said. “You don’t see that too often.”

Daniel Murphy tormented his former team with a 3-for-4 performance that included two homers and six RBIs to lead the Nationals’ 26-hit attack. The Nationals scored seven runs in the first inning and kept attacking, padding that lead to 10-0, 13-0, 16-0 and 19-0 after the second, third, fourth and fifth innings, respectively. The Mets finally offered resistance with a scoreless sixth and seventh.

Murphy, Trea Turner, Juan Soto, Anthony Rendon and Michael A. Taylor all had at least three hits for the Nationals.

Jacob Rhame, Tim Peterson and Tyler Bashlor were all clobbered in relief behind Matz, who didn’t even survive the first inning.

In the shortest outing of his career, Matz lasted only two-thirds of an inning and allowed seven earned runs on eight hits and one walk. The lefty, who was among the players the Mets made almost untouchable at the trade deadline, allowed two hits to Turner in the first inning alone.

“I think I am going through a thing and trying to work through it,” Matz said. “This stuff comes up throughout the season and I just have to find a way to find a way to get through it and I wasn’t able to do that today.”

When asked if the “stuff” was fatigue, Matz did not offer specifics.

“It’s just stuff you go through during the season,” he said. “Good pitchers find a way to get through it and that is just what I am trying to figure out right now.”

A club source indicated the lefty was dealing with dead arm — which is not uncommon this time of the season.

It was a third straight unsatisfactory start for Matz, whose ERA has surged from 3.31 to 4.35 since July 12.

Tanner Roark’s bases-loaded double for three RBIs was the Nationals’ biggest hit in a first inning that wouldn’t end. Matz was mercifully removed after 32 pitches. The seven runs allowed by Matz matched a career high.

“[Matz] was leaving everything over the middle,” Callaway said. “Everything was leaking back over the middle of the plate. It was up and they did some damage.”

Jeff McNeil ensured the Mets wouldn’t get shut out by hitting his first major league homer, a solo blast with two outs in the seventh. Austin Jackson hit a two-run blast in the ninth inning for his first homer with the Mets; the veteran outfielder was signed on Friday.

Roark dominated the Mets, holding them to one run on four hits over seven innings.