Dom Hamel learned a new pitch.

It took several more months for Hamel to learn the control, mindset and confidence needed to maximize his added weapon.

The Mets’ starting pitching prospect worked on a sweeper this spring, encouraged by pitching-development minds who saw how well Hamel can spin a baseball.

Hamel’s spin rates are some of the best in the organization, a unique ability that has especially enhanced his four-seam fastball, curveball and more traditional, tighter slider.

There were times during the first half of the season when Hamel wanted to give up on the sweeper, which he saw had excellent horizontal movement but perhaps too much — it was hard to harness and hard to throw for a strike.

The occasional spinner would not move much and then would get crushed. In his first 17 starts with Double-A Binghamton this season, Hamel posted a 5.09 ERA with 32 walks in 76 innings.

The more he threw it, though, the better Hamel could command it.

With the better feel came a better confidence — not just with the new offering but with his full repertoire.

The new attitude?

“Let me just throw the s–t out of everything in the zone and just challenge everyone,” Hamel said this week from Binghamton, where his Double-A club fought for an Eastern League Championship. “Screw being all cutesy and tedious around the zone.”

And with that he took off, ripping off nine starts to finish his regular season in which he allowed 10 total runs for a 1.88 ERA.

He struck out 61 and walked 17 in 48 innings, ascending in a rotation that suddenly was filled with intriguing talent.

Hamel — along with his rotation mates this season in Blade Tidwell, Christian Scott, Tyler Stuart and Mike Vasil, who finished the season at Triple-A Syracuse — is a reason for hope for a Mets starting pitching pipeline that has been clogged.

The Mets have struggled to develop starting pitchers since their rotation was filled with Jacob deGrom, Matt Harvey, Noah Syndergaard, Zack Wheeler and Steven Matz.

Progress out of the new pitching lab in Port St. Lucie and identifying new pitches for pitchers such as Hamel would bode well for the organization’s future.

Hamel long has been an enticing pitcher because of his ability to manipulate the ball.

He mostly played the outfield in high school and was hesitant about his pitching talents with a low-90s fastball.

But at Dallas Baptist, he learned his best pitching gift did not involve velocity.

“I know I have a low release height and good extension and [good] ride, so [my fastball] looks like it’s coming down and just takes off even more,” the 6-foot-2 right-hander said. “That’s been the coolest part to learn so far from pitching. You see dudes that are 98 [mph], and they’ll get touched sometimes, and our hitters will come in and they’re like, ‘That’s the slowest 98 I’ve ever seen.’

“And then they face a guy who has a similar fastball to me — something that’s not as hard in terms of velocity — but it’s got more spin and more jump to it. And they’re like, ‘That’s the hardest 92 I’ve ever seen.’ ”

The Mets drafted Hamel in the third round in 2021, and he impressed with a 3.25 ERA in 119 innings split between Low-A St. Lucie and High-A Brooklyn last season.

This year became about developing the sweeper, finding the right pitch mix and, eventually, attacking the zone.

“Oh my God,” Hamel remembers thinking when he struggled to throw strikes, “I need to start pitching differently because of this new pitch. I can spin the crap out of this pitch. It might not necessarily go exactly where I want to in the zone. … But the shape’s too good not to put it in the zone and see what happens.”

It was Hamel who got the ball in Thursday’s clinching, Game 2 victory in the Division Series over Somerset, in which the 24-year-old shut out the Yankees’ affiliate for 7 ²/₃ innings in which he allowed just three hits and two walks while striking out eight.

Hamel has learned to trust his stuff, which has improved, and the Mets have more trust in a group of pitching arms who are coming along well.

“We all trust in each other to figure our s–t out, and we’re able to help each other figure s–t out,” Hamel said of the Binghamton rotation. “It’s a well-knit group of guys all around. We all push each other, we all believe in each other to go out there and shove against anyone.

“There’s really a why-not-us feeling.”