Mets pitcher Jeurys Familia delivers in the top of the...

Mets pitcher Jeurys Familia delivers in the top of the ninth inning against the Phillies at Citi Field on Wednesday. Credit: Errol Anderson

WASHINGTON — When Jacob deGrom exited the Mets’ game Thursday after six innings and 86 pitches, 15 pitches fewer than his previous game, it didn’t bother him. He was beat after a long final frame and he knew what came next: a dominant bullpen.

Four relievers held the Nationals scoreless the rest of the way in the Mets’ 8-2 win, running the bullpen’s string of shutout innings to 13.

“It’s definitely a plus,” deGrom said, “when you’re comfortable handing over the ball to the bullpen and know they’ll hold on to a lead for you.”

In this season-opening hot stretch for the Mets, it has been the bullpen — more than the good-but-not-great starting pitching and pretty strong lineup — that has been most effective, the start of a potential rebound after the Mets had perhaps the worst relief unit in the National League in 2017.

The Mets’ relievers entered an off day Friday with the best WHIP (0.94) and batting average allowed (.160) in the majors. Their 1.16 ERA was second behind the Cubs’ 0.62.

Of the three earned runs the bullpen has allowed in 23 1⁄3 innings, one came against Anthony Swarzak (disabled list, strained left oblique) and two came against the two relievers at the bottom of the depth chart, Paul Sewald and Jacob Rhame.

Everybody else — late-inning mainstays Jeurys Familia, AJ Ramos and Jerry Blevins, converted starters Robert Gsellman and Seth Lugo, and even Hansel Robles — has posted zeros.

“It’s been fun to watch them,” manager Mickey Callaway said. “Confidence plays a huge deal in everything, and obviously they’re confident right now. Them having confidence gives us confidence to put them out there in whatever situation. I think they all are aware they need to be ready at all times.”

That is Callaway’s first commandment of being in the bullpen: Be ready to pitch in any inning. The game is moving away from strict relief roles — closer, eighth-inning guy, long man — and Callaway and pitching coach Dave Eiland are pushing the Mets in that direction.

Gsellman and Lugo, who traditionally would be the most logical picks for the long man/mop-up roles, have had short appearances in close games. Ramos, a closer for years in Miami, recently pitched in the sixth (against the top of the Phillies’ lineup) for the first time since 2015. Familia, who has received all three of the save opportunities, last week nailed down his first with four outs and 30 pitches, a rare feat in late March.

Another modern idea that Callaway subscribes to, that it’s better to go with a fresh mediocre reliever than a fatigued starting pitcher the third time through the lineup, means shorter outings for the starters and more innings for the relievers.

That’s fine by Blevins, who said Callaway has effectively stressed to the relievers the need to be ready.

“We understand that we’re going to pitch and we’re going to pitch often,” Blevins said. “We’re just ready to go. Everybody is always locked in. There are no big egos down there.

“If the manager is open and [says to] be ready at any given point, that’s your job going in. He treats us like we’re men. ‘This is what I’m going to ask of you. If you can’t do it, we’re going to get somebody else.’ So everybody is ready to go.”

The additions of Lugo, who opened the year in the rotation but did not make a start, and Gsellman have been key. Gsellman struck out the only batter he faced Thursday after tossing two scoreless innings Wednesday — his first time pitching back-to-back days.

It was definitely different, he said. And he was tired. But that’s part of learning how to be a reliever.

“Felt good to get the first one out of the way,” Gsellman said. “Many more to come.”

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