David Peterson’s success story this season doesn’t revolve around developing a new pitch or changing much about his approach.

Simply, the Mets left-hander is pain free. It’s opposing teams that are feeling the pain instead.

“I think that has made the biggest difference,” Peterson said Friday at Citi Field, referencing the left hip labrum he had surgically repaired after last season. “That subsequently has cleaned up some stuff all the way up the chain through my torso and upper body.”

The results have been beyond anything the Mets could have anticipated.

Peterson, in 17 starts for the team this season, is 9-1 with a 2.75 ERA and only improving as the season has progressed.

His signature performance this year might have occurred Tuesday when he struck out a season-high 11 batters against the Red Sox, allowing one earned run over six innings.

The Mets have Sean Manaea and Luis Severino performing at ace-like levels and Jose Quintana enjoyed a midseason hot streak, but Peterson has been the steadiest rotation presence for a team that began the day tied with Atlanta for the National League’s third wild-card spot.

“The more [Peterson] goes out there, I think he knows that he not only belongs in this league, but he can dominate,” manager Carlos Mendoza said.

Peterson bounced last season between Triple-A Syracuse and the Mets and the rotation and bullpen.

He pitched to a 5.03 ERA in 27 appearances for the club and decided after the season it was time to address the hip that had caused him discomfort at various points.

“Rotating properly and without pain is the biggest thing,” said Peterson, whose November surgery kept him rehabbing until late May.

The metrics paint a different picture than somebody who has succeeded this season: Peterson’s percentile rankings on baseball savant are largely blue, denoting below average for a certain category.

Those blue numbers (walk rate, strikeout rate, hard-hit ball rate, expected ERA, expected batting average) suggest a pitcher that has received his share of luck this season, a fact Peterson won’t deny.

But he’s not about to apologize for his success.

“They obviously have a certain algorithm and scale that everything runs on and there’s some truth to it,” Peterson said. “There’s probably some stuff where the numbers don’t necessarily align with the way I have been pitching and I don’t take it too much to heart.

“It’s stuff that I look at because it’s a good resource, but it’s not like I look at it and see a lot of blue and start freaking out because I’m seeing myself go out there and do it every five days and that alone gives me the confidence. My stuff may not grade out well in their categories, but it’s getting guys out.”

Among the differences in Peterson’s pitch usage from last season is an uptick in deploying the sinker (from 25.3 to 31.3 percent).

The result has been an increase in ground-ball percentage — one of the few red numbers that appears on his Statcast profile.

Peterson’s ground-ball percentage of 52.8 ranks in MLB’s 90th percentile.

“I have some stuff that lends to getting hit on the ground, whether it’s the sinker or the changeup, and then I think it’s just been the sequencing and our plan of attack with guys and knowing the right spots to get the ground ball when we need it,” Peterson said.

Peterson’s emergence means the Mets will have one less headache this winter in building a rotation for next season.

Severino and Quintana are headed to free agency and Manaea will almost certainly opt out from his contract.

Peterson is under club control for another two seasons.

“I have still got some time left in terms of control and I love being here,” Peterson said. “I want to be in this rotation and pitch every fifth day for this team.”