The Mets' Starling Marte salutes teammates as he rounds third on...

The Mets' Starling Marte salutes teammates as he rounds third on his solo home run off Atlanta pitcher Jake Odorizzi during the first inning of a game Wednesday in Atlanta. Credit: AP/Curtis Compton

PHILADELPHIA — Starling Marte has been effective for the Mets in virtually all areas, producing as a well-above-average hitter and transitioning seamlessly to rightfield. It made him an All-Star last month and has more than validated the first season of the four-year, $78 million deal he signed last offseason.

He is never more effective, though, than in the first inning. His absurd splits included a .375 average, a .415 OBP and a .659 slugging percentage — plus seven of his 14 homers — in the opening frame heading into the Phillies series (Marte lined out in his first at-bat Friday).

“If we could teach that to everybody . . . ,” manager Buck Showalter said. “Starling is always firing. Not real sure [why the first inning is so different], but I’m OK with it. The damage is pretty good.”

The Mets happily will take that production, even if it is difficult to pin down why that has been the case. Last year he was terrible in the first inning. In his career, he is a .269 hitter with a .729 OPS in that spot — markedly worse than his overall numbers. Marte’s theory: He has been able to take advantage before the opposing starting pitcher gets a chance to settle in and feel out the game.

“Honestly, I just focus on my approach and try to hit the ball up the middle,” Marte, who did that Wednesday when he homered to centerfield, said through an interpreter. “As the game goes on, pitchers are able to start reading swings, so they start making their adjustments as well. In that first inning, they’re not necessarily able to read the swings as well.”

This season has been successful in a different way than Marte has been accustomed. His 14 homers already are two more than he had last year (and in 19 fewer games). But he also is stealing fewer bases than usual, his 15 entering play Friday putting him on pace for the lowest full-season total of his career.

One reason: His legs have not been totally healthy. He missed several days because of a left quadriceps problem in June, then a few more days with a left groin problem in July — and those are only the injuries that are public knowledge.

His recent basepath behavior offers a hint, though, that he has felt fine of late — and it showed Friday night in the fifth inning. Marte stole home as part of a double steal with Francisco Lindor. In the past two weeks, he has swiped three bases (in four attempts). In the two weeks before that, even after resting because of his groin, he didn’t try to steal at all.

That is in part, he said, because his legs have been better over that stretch.

“From the standpoint of stealing bases, it’s been tougher on me this year,” Marte said. “Just with the injuries that I’ve had to my legs, it’s been a little bit tougher — especially with the groin and stuff like that. You really have to play it smart because you’re not trying to miss the rest of the season.”

That point is worthwhile, echoed by lots of Mets players and personnel in the context of all sorts of injuries. In the case of Marte, whose strong throwing arm highlights his adept play in right, it is particularly important. The Mets don’t have a ready-made replacement in the event he missed significant time.

And so he plays it safe.

“There have been days where I’ve felt really good,” he said. “There are other days not so much, where I’m really just trying to get secondary leads, so when the hitter puts the ball in play, I’m able to put myself in a position to score.”