The Mets' Pete Alonso returns to the dugout after he...

The Mets' Pete Alonso returns to the dugout after he flies out against the Dodgers during the sixth inning at Citi Field on Sunday. Credit: Kathleen Malone-Van Dyke

Pete Alonso carried the Mets through some of their darkest periods this season, repeatedly dragging them back into the spotlight of respectability almost singlehandedly.

Sunday night was the first time that Alonso seemed to strain under that weight — when the responsibility of being the affable Polar Bear, the likely Rookie of the Year and the potential home run champ actually looked as if it felt heavy on his broad shoulders.

After the Mets’ 3-2 loss to the Dodgers, a sobering defeat that dropped them four games back in the wild-card race with 13 games left, Alonso stood at his locker and performed a duty he’s frequently done in joyful circumstances.

But he has never been forced to reflect on something like what he’s going through at the moment. Sunday’s 0-for-4 extended his drought to 0-for-20 with 10 strikeouts — the longest of this season, at the worst possible time, with the Mets’ playoff hopes dimming.

“It’s been a rough week,” he said.

Alonso is one of the most accomplished rookies in Mets history, but he still gives off the vibe of unfinished business with his high motor and relentless preparation. Mickey Callaway recently described him as the team’s “energy drink,” and the Mets’ addiction to that fuel is the reason he played in his 148th game Sunday night — the most of any rookie and one off the pace of a seven-man lead pack.

“We have a chance to do something great,” he said before the game. “I feel like if we continue to come here with a really good intensity, good things are going to happen. I think that everything for me is all about controlling the effort level every single day.”

There is no questioning Alonso’s effort. It’s more the toll of what must be an exhausting year. Last season, splitting time between Triple-A Las Vegas and Double-A Binghamton, he totaled 132 games, then tacked on an additional 27 in the Arizona Fall League, where he was introduced to new general manager Brodie Van Wagenen, one of his earliest fans. But not even the smitten GM imagined this dream season or how irreplaceable Alonso would become.

He’s hitless since going deep twice in Monday’s 3-1 victory over the Diamondbacks, and the echoes of his 47 home runs (only five short of Aaron Judge’s rookie record) ring louder each time he comes to the plate. On Sunday, Alonso flied out twice, drawing a hopeful gasp from the Citi Field crowd before the ball died somewhere in the medium-depth outfield.

Afterward, the inevitable question was posed: How is he feeling?

“It’s been tough,” he said, “but I feel fine.”

Callaway saw signs of fatigue when he chose to rest Alonso for Friday’s opener with the Dodgers, but the move still spurred mild outrage. Alonso, 24, is at an age at which you can be oblivious to such things until someone points them out, but he’s smart enough to listen.

“I obviously want to play every possible game,” he said. “I don’t think I ever need a break because that’s just the type of person I am. Once I’m in the zone and once I’m in the thick of things, it’s kind of hard to take a step back and glance at things outside of the fishbowl.”

Alonso often has been the face of the franchise on top of what he’s provided between the lines: his MLB-leading 47 home runs, 109 RBIs (ranked seventh) and .582 slugging percentage (ninth). He is the rare player who can make it all look so easy when it is anything but, but this is uncharted territory for him.

“It’s a different grind up here at the major league level — mentally, physically,” Callaway said. “But they don’t even think about it. They just keep on going, going, going until they either blow out or you say hey, you’re off today.”

Fortunately, it was the latter scenario with Alonso, and he’s been cognizant of keeping his strength up over the course of the past seven months. You wouldn’t expect that to be a problem for a guy built like a stack of beer kegs, but Alonso doesn’t crush baseballs by accident. It takes maintenance.

“I always try to eat a lot and sleep a lot,” he said Sunday afternoon. “Everything’s focused on 7:10 that night. For me, it’s just all about winning. I don’t want to do great for Pete Alonso. I want to do great for the New York Mets. It’s a big thing we got going on and I feel like something special is going to happen. I just want to do everything I can to help.”

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