Mets pitcher Zac Thornton throws in the first inning of a...

Mets pitcher Zac Thornton throws in the first inning of a game against the Boston Red Sox at Citi Field on July 12. Credit: Thomas A. Ferrara/Thomas A. Ferrara

MILWAUKEE — Zac(h) Thornton has been living a lie.

OK, well — not really, but if you happened to peek at the Mets’ roster Monday afternoon, you may have noticed that an extraneous ‘H’ had disappeared from the young lefthander’s name, despite the fact that Zachary Charles Thornton has gone by ‘Zach’ his entire professional career.

But this was no rebrand. It turns out Zac — now slotted into the rotation after a brilliant performance against the Red Sox to close out the first half — is simply showing the world who he's always been.

“I’ve actually been wanting to do this for a while,” he told Newsday a day ahead of his scheduled start against the Brewers — the fourth of his career. “I never understood what the ‘H’ really did at the end of it. My whole life, I’ve always wanted Zac and I’ve always written it down like that.”

So, was the change the result of some newfound confidence? The belief that you’ve got the stuff that can play at the major-league level? Of finding belonging in baseball’s highest level?

It’s not quite as poetic as all that.

“They don’t approach you about that in Triple-A,” he said.

That, though, means something, too. A few weeks ago, no one was asking Thornton how he wanted his name spelled. And now, he’s gone from being an interesting, under-the-radar lefty to a player worth paying rapt attention to, and another reason to believe this team’s young pitchers can key them to future success. He’ll also be thrown into a downright Shakespearean showdown Tuesday, when he’s set to take on Brandon Sproat, whom the Mets traded to the Brewers in exchange for Freddy Peralta.

Sproat, who got off to a rough start, has a 2.45 ERA over his last four starts, and you can certainly believe that if he continues on that trajectory, there will be no shortage of fans bemoaning the move that netted them a rental who is likely to be gone by the trade deadline.

But things like that don’t seem to faze Thornton, whose ease is evident in his mannerisms, both in the clubhouse and on the mound. After allowing four runs in the first 1 1/3 innings of his major league debut in May, he’s given up just one run in the next 16 innings, and he’ll only benefit from the routine afforded to him by having a consistent slot in the rotation. He has a 2.60 ERA and a 0.92 WHIP, and his seven scoreless innings against the Red Sox before the All-Star break was among the best by a Mets pitcher this year.

He displays the hallmarks of the fearlessness that has allowed both Nolan McLean and Christian Scott to have early success, despite that up here, “teams are ready to hit,” he said. But Thornton was built in the mold of the old school, soft-tossing lefty, where playing scared means your stuff doesn’t play at all.

“I do a really good job of living on the edges of the strike zone and try my hardest not to leave pitches down the middle because you obviously get burned for those,” he said simply. “I think the one thing I’ve done in my life is work on command and control. I think when I was young — 13 or 15 years old, my dad and I would play catch together and he’d go out to 90 feet and I would throw a bullpen from 90 feet. He’d say, ‘If you can throw a strike from 90 feet…You’ll be able to do it from 60 feet.’”

That alone will teach a kid the value of listening to your elders, and Thornton has continued that trend here, where he’s tapped fellow lefty Sean Manaea for pointers. Manaea, in turn, has been impressed by Thornton’s mentality, “and the relentless kind of attacking,” the veteran told Newsday.

“Every time I’ve seen him, I’ve seen him” do that, Manaea said. “It’s [gutsy]. I know how hard it is and he makes it look easy.”

Mostly, he tries to help Thornton and many of the other young pitchers understand the intricacies of the major-league routine, but in typical fashion, tries to do it in an unintrusive way.

“I’m not here to say this is the only way to do things or that my way is the right way,” Manaea said. “It’s more like, ‘I take pride in my work and if you resonate with that, then it’s cool, and you can figure things out on your own…But [when it comes to the routine], it’s a long season. For me, you’ve really got to trim things down a little bit [and] find stuff that works.”

Thornton has done that figuratively, and Monday, did it literally, evicting the ‘H’ that added nothing to his first name.

“It feels good,” he quipped. “I’m out of my shell now.”

That could end up being true in more ways than one.

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