Michael Fulmer played with Jacob deGrom, watching as deGrom clawed his way back from Tommy John surgery and discovered his curveball, finally staking his claim in the Mets’ rotation. He saw Noah Syndergaard and then Steven Matz, once his teammates, make their major-league debuts and live out a dizzy postseason dream in their rookie years.

And Fulmer waited.

He waited while his knee and elbow betrayed him, requiring three surgeries and leading to questions about his durability. He waited while his name, once said in the same breath as deGrom, Syndergaard and Matz, became a footnote in the Yoenis Cespedes trade last year — making him a sort of Forrest Gump of the 2015 Mets’ Greatest Hits.

Finally given his shot with the Tigers this year, he has showed a different sort of patience. While others wondered if Fulmer was overmatched in the big leagues and if his somewhat mediocre start portended the pitcher he was going to be, he worked tirelessly on his third pitch — a changeup — and possibly changed the course of his future. In the process, he has shown that the trade that sent him to Detroit has hardly been one-sided.

“It’s been a roller coaster, it really has,” Fulmer said. “The injury bug hit me a little bit. Those guys [on the Mets], all five of them are great pitchers, with [Matt] Harvey and [Zack] Wheeler as well — great pitchers, great friends, great teammates. It would have been an honor to pitch alongside them, but as of right now, I’m happy that I’m not there anymore because those guys are all All- Stars, pretty much. I’m extremely happy with where I’m at now with this team. I love this team.”

At this time last year, Fulmer was a Binghamton Met, but he is scheduled to take the mound Sunday at Yankee Stadium wearing a Tigers jersey. And more than the uniform has changed for the 23-year-old right- hander, who has been nearly untouchable in his last four starts, causing a buzz reminiscent of his former teammates.

He had a 6.52 ERA in his first four starts before a pivotal bullpen session in which he threw about 30 changeups — a third option after his fastball and slider. “Something just clicked,’’ he said. “I can’t tell you what because I had no idea . . . [but] ever since, it’s been working.”

No kidding. Since that session, Fulmer is 4-0 with a 0.32 ERA. He hasn’t allowed an earned run in 22 1⁄3 innings since May 21, a three-start span. In his last 28 1⁄3 innings, he’s allowed 11 hits and struck out 27.

“The talent is off the charts. Anyone can see that,” said catcher James McCann, whom Fulmer credits with his success, along with backup Jarrod Saltalamacchia. “What really stands out is his willingness to learn and his willingness to prepare . . . There’s a lot of young talent in this game that thinks they’ve got it all figured it out. He’s the exact opposite. He’s a young talent that wants to continue to learn. He’s a sponge.”

McCann indeed was pivotal in Fulmer’s progress. The two set up a game plan for his changeup, which has allowed Fulmer to evolve in how he uses the pitch. They’d throw it early in counts, in low-stress situations — first pitch with two outs, for example — until he developed a feel for it.

Fulmer, who said he’s had his changeup since 2012 but didn’t use it often, said it’s changed the tenor of his game.

Tigers manager Brad Ausmus called the “rapid development” of Fulmer’s changeup a “huge plus.”

“They’re doing a great job of calling it more often, and if I don’t like the pitch, I can shake to it or shake from it,” Fulmer said. “It just gives them more options, and I kind of trust them to do more nodding than shaking . . . I like to take the mound and do as little thinking as possible, and that trust we build with Mac and Salty, it’s been unbelievable, and hopefully they trust me as much as I trust them.”

The success that’s come is not necessarily something Fulmer envisioned, though he’s not short on confidence. He distinctly remembers when he heard about being traded. He was called into Binghamton Mets manager Pedro Lopez’s office and came out to the hoots and hollers of his teammates, who were looking at his face and name plastered on MLB Network.

To everyone else outside that room, Fulmer was just a trade chip, but for him and teammates like him — guys who had seen deGrom, Syndergaard and Matz pass through, along with many others — it represented something completely different: a future. “There’s the new Tiger,” he recalled them yelling.

“It was kind of out of nowhere,” he said. “That moment was kind of surreal. It was nice to be wanted.”