The Mets’ Rajai Davis trots home after his three-run homer ended Sean Doolittle’s night and capped a six-run New York eighth. The Nationals dropped their fourth straight, 6-1. (Kathy Willens/Associated Press)

This was the reliable reliever — the one reliable reliever — the Washington Nationals have leaned on and leaned on and leaned on with all their weight whenever they had to.

But here Sean Doolittle was, standing just off the Citi Field mound, his hat tipped back, his head shaking slowly in frustration as a crowd roared around him. New York Mets center fielder Juan Lagares had just rocketed a down-and-in fastball into the left-center gap with two outs in the eighth inning, kick-starting a carousel on the base paths. Three runners scored. Lagares stood on second, his arms flapping for more noise, and the Mets went on to win, 6-1.

They tacked on three more runs when Doolittle gave up a home run to Rajai Davis three batters later. The Nationals’ closer came into the game with a 1.71 ERA, eight saves and a reputation as the only trustworthy pitcher in the league’s worst bullpen. He left it having let six runs score without recording an out, disbelief spread across his face, his team sputtering to a 19-30 record and a chance of getting swept here Thursday.

“I’m really frustrated,” Doolittle said in a funereal clubhouse afterward, his eyes near blank behind a pair of glasses. “I’m disgusted with myself. I let the team down, and it hurts.”

“It was shocking. That’s a good word for it,” Manager Dave Martinez said. “He’s the best, the best we have.”

The Nationals’ clubhouse was quiet by night’s end, with no music playing, no conversations outside of interviews, no one quite knowing what has gone so wrong. They had a team meeting before the game, talked about accountability and trust and stressed the importance of not pointing fingers while they weather this weeks-long storm. Martinez told reporters that there has to be belief. He pointed to the 113 games remaining on the schedule. He reached for hope — beyond reason, beyond anything else — that the Nationals’ best days are ahead.

But that vision hasn’t materialized. The season kept pushing the Nationals around Wednesday, this time with four outs to go, and left them still stuck in a search for answers. Right fielder Adam Eaton, who homered off Mets starter Jacob deGrom for the Nationals’ only run, had trouble coming up with new ways to describe the situation. Doolittle rubbed his neck when asked how he felt, looked into the carpet by his feet and spoke slowly and softly as he expressed shock of his own.

And Scherzer, one of the team’s veteran leaders, stood by his back-wall locker and talked loudly enough for nearby teammates to hear. He had a message. The Nationals are 2-9 in his starts, and just about everything has to change.

“No one likes to lose. Everyone hates losing. Everyone in here hates to lose,” Scherzer said. “You don’t have time to feel sorry for yourself. You got to come out tomorrow and just compete. There’s nothing else you can do.”

“When you face adversity, this is when you reveal yourself,” he continued. “Whether you have the mental fortitude to come and you can block out all the negativity that’s probably going to surround us right now.”

They nearly sidestepped all their trouble, at least for one night, after Scherzer exited after six scoreless innings and the Nationals held a one-run lead. Scherzer went pitch-for-pitch with deGrom, the Mets’ ace and reigning National League Cy Young winner, and put his team in position to rebound from three straight losses.

But Scherzer’s pitch total spiked in the early innings and, by the end of the fifth, was up to 98 as he stomped toward the dugout, jaw clenched, right arm bouncing with each step. He went one more, gutting out the sixth with 11 more pitches, and now Washington’s bullpen had to get nine outs for a win.

It is unfair to ask for more than that from Scherzer, who had tossed 108, 101, 110, 112, 115 and 112 pitches in his six starts leading into Wednesday. But that’s how unreliable the Nationals’ bullpen has been. On Tuesday, after a strong outing from Erick Fedde, it blew a one-run lead and a two-run lead and then allowed the Mets to walk off with a win in the ninth. The challenge, then and always, was getting the ball from the starter to Doolittle.

But Martinez pressed the right buttons Wednesday, plugging Joe Ross in for one hitter, Matt Grace for two, Kyle Barraclough for two outs in the eighth and, once he put two runners on, Doolittle for the end. Doolittle just couldn’t finish the job. He hit Carlos Gomez with his first pitch, missed his spot on Lagares’s double, intentionally walked Wilson Ramos and gave up the backbreaking homer to Davis.

The Nationals have lost in so many ways this season, but Doolittle had been one of the few players they could count on. So this was different. In a blink, in the span of four batters and 12 fateful pitches, the game went from winnable to a new low.

“It’s a tough spot to come in,” Doolittle said. “And with the context of how our season is going, it hurts even more.”