WASHINGTON — Jeurys Familia’s fastball crackled at 96 mph and moved with the same life as it had before surgery. But there is no replacement for dealing with the adrenaline of pitching in big-league games.

So it mattered little in Saturday’s 9-4 loss to the Nationals that Familia has pitched in the World Series. Or that he’s racked up 103 saves while becoming one of the league’s top closers. Or that he was pitching in a non-save situation to get his feet wet in a meaningless August game — at least for the Mets.

In his first game action since undergoing surgery to address a blood clot, Familia allowed three runs on four hits in one inning, during which it was clear that he may need more time to regain his command.

“I think I tried too much today,” said Familia, who last pitched for the Mets on May 10.

Familia entered in the eighth inning, with the Mets trailing 6-4 thanks to another rough outing by Robert Gsellman. The righty allowed six runs — two earned — and lasted just four innings.

Reliant on keeping his two-seamer low in the zone, the righty surrendered nine hits, many on pitches up in the zone. He also dropped a feed from Wilmer Flores while covering first base in the first inning, opening the door for the Nationals to score four unearned runs.

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After two encouraging outings following a stint on the disabled list with a hamstring injury, Gsellman delivered a clunker, following a pattern of inconsistency that has played out all season.

“It’s been tough but you’ve got to keep your head up,” said Gsellman, who is 5-6 with a 5.60 ERA after emerging as a second-half savior last season.

The latest setback will cost him his spot in the rotation — at least temporarily. Following the game, the Mets optioned the 24-year-old Gsellman to Triple-A Las Vegas to make room for Seth Lugo, who was activated from the DL to start the nightcap of Sunday’s doubleheader.

Gsellman won’t be eligible to return until after Las Vegas’ season ends on Sept. 4.

Meanwhile, manager Terry Collins as expected waited to ease Familia back into game actionin a non-save situations, which is why he entered in the eighth with the Mets trailing 6-4. But despite a fastball that consistently hit 97 mph, he lacked command.

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Adrian Sanchez, Wilmer Difo and Adrian Sanchez each had run-scoring singles off Familia, whose ERA rose to 6.10. Sanchez’s hit came after he wound up face-down on the ground for more than a minute. He had initially squared to bunt. But Familia fired a 96 mph fastball that hit Sanchez’s chest.

“I feel bad because I don’t want to anybody,” he said. “I just want to do my job.”

The pitch counted as a strike. Rattled, Sanchez dusted himself off, then lined another Familia fastball to left to extend a rally. The Mets (56-72) fell to 16-25 since the All-Star Break, their season reduced to playing out the string.

“My sinker had the same [movement] as I’ve had always,” said Familia, who surrendered four hits and three walks. “Just, I missed the zone a couple of times and I didn’t have my command.”

But Familia did have full feeling in his fingers and none of the numbness that sent him to the DL and eventually for surgery. Fully healthy, the reliever believes he’ll need a few more appearances before regaining hi command.

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“It’s just a little bit different,” he said. “It’s not the same adrenaline between the minor leagues and the major leagues. But I’ve been in that situation before . . . I know I can do better.”