NEW YORK — First-year Mets manager Mickey Callaway knew something was wrong when Wilmer Flores went to the plate for the first time. But by then it was too late to correct.

The Mets wasted a first-inning rally by batting out of turn, and Adam Duvall led off the 10th with a homer that sent the Reds to a 2-1 victory Wednesday and gave them just their second series win this season.

“It is frustrating,” said Callaway, who blamed himself for an administrative mistake. “It probably cost us a game. We had a chance to score in the first and we didn’t.”

The Reds took advantage. Duvall connected for the first game-ending homer of his career off A.J. Ramos, sending the Mets to their eighth loss in nine games.

Callaway’s lineup card handed to the umpires had Asdrubal Cabrera batting second and Flores third. However, the lineup sent out by computer pregame and posted on the dugout wall incorrectly had the two hitters switched in the order. Callaway didn’t identify who sent out the incorrect lineup.

After Flores batted out of turn and struck out for the second out, Cabrera doubled to left. The Reds quickly pointed out the discrepancy, the double was nullified and an out was called.

“I felt bad,” Reds interim manager Jim Riggleman said. “It’s so easy to have that happen.”

Crew chief Jerry Meals had never dealt with a batting-out-of-turn incident in the majors but had seen it occur in the minors.

It was the first time since 2016 that a major-league team was caught batting out of turn. The last time the Mets did so was 1977.

“Some weird baseball,” Mets pitcher Zack Wheeler said, “but it does happen every once in a while.”