Brandon Nimmo #9 of the Mets runs to first base...

Brandon Nimmo #9 of the Mets runs to first base during a game against the Washington Nationals on Opening Day at Citi Field on April 4, 2019, in Queens. Credit: Jim McIsaac

Mickey Callaway planned to give Brandon Nimmo a mental break Sunday against Max Scherzer and the Nationals at Citi Field. So at the beginning of the game, the Mets’ slow-starting leadoff man was left out instead of out in left.

Zack Wheeler left his command at home, though, and Nimmo’s break ended with two outs in the top of the fifth because of a double switch.

After flying out to center in the bottom half, Nimmo stood in against Scherzer in the seventh with no hits in his last 13 at-bats and two hits in 27 at-bats overall. Then he lined an RBI double to right for his first extra-base hit of the season, ending the three-time Cy Young Award winner’s day.

Nimmo also made solid contact on a liner to right-center that was caught in the ninth inning of the Mets’ 12-9 loss.

He didn’t pronounce himself cured, but Nimmo is sure he will be at some point. His belief in himself hasn’t taken a hit.

“Whether it’s right or wrong, I have a lot of confidence in what I did last year,” he said. “I think with last year under the belt, I know that I’m completely capable, and not just at being adequate at this level, but being highly successful at this level.

“And so I think it’s just a matter of time . . . As long as I prepare and work hard, I think eventually it’s going to turn around.”

Callaway called Nimmo’s work at the plate one of “the silver linings” of the day, saying, “He looked a lot better than maybe he had previous.”

Nimmo hit .263 with 28 doubles, eight triples, 17 homers and 47 RBIs in 140 games last season. He finished second in the National League and fourth in the majors with a .404 on-base percentage and was ninth in the league with 80 walks. He probably also finished first in the majors in smiles.

But it was hard to be the happiest man in baseball when he showed up at the stadium with a .077 average and one RBI.

“It’s the high fastballs and the breaking balls below the zone,” Callaway said before the game. “He’s missing them . . . It’s been a rough go.”

It’s very early, though. He’s up to .103 for a team that’s 6-3.

“He’s a really good hitter,” Pete Alonso said. “I know he’s going to be fine.”

Nimmo said he has studied video “for many days and many hours.” He knows he has been chasing pitches. While he downplayed the double, saying Scherzer was tired at that point, he did take a bit of encouragement from it and the final at-bat.

“You try and find good pitches in the zone and then try to put them in play, and I was able to do that twice,” Nimmo said. “So it’s definitely a step in the right direction. But by no means is it like, ‘Oh, yeah, we’ve definitely figured everything out.’ ”

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