Part of the reason Isaiah Hartenstein chose Oklahoma City was an opportunity to “expand my game a lot,” he said Saturday — specifically, showcase an offensive skill set that wasn’t encouraged by the Knicks.

“If you’re an NBA player, you have to adapt to certain roles. And that’s what I did in New York,” Hartenstein told reporters after officially inking his lucrative deal with the Thunder. “My passing only came out in the last year. My first year, I had to adapt to a certain role. So I feel like I can get back to that shooting aspect. Before, I was shooting, so I want to get back to that even more.”

In his first season with the Knicks in 2022-23, Hartenstein wasn’t shy about his difficulty adapting to the limited offensive role of a center in Tom Thibodeau’s system — which was mostly predicated on screening and rebounding. It was different at his previous stop with the Clippers, where Hartenstein hit the occasional 3-pointer at a strong percentage and racked up more points and assists per minute. Hartenstein had more opportunities with the ball last season, as he mentioned, but the 26-year-old believes Thunder coach Mark Daigneault will enhance his game.

“I’ve been in a lot of situations. I know how to adapt,” he said. “But the way they play here is really exciting for me. It can expand my game a lot, especially offensively.”

Of course, the other big factor was money. The Knicks were capped at an offer of four years, $72.5 million, which they kept on the table until Hartenstein signed elsewhere. The Thunder gave Hartenstein a three-year, $87 million contract — though the final season, as The Post reported, is a team option. The guarantee is two years and roughly $58 million — or about an $11 million higher average salary than the Knicks’ offer.

It was a difficult decision for Hartenstein, who had a guaranteed starting spot in New York and chemistry with his teammates. His role in OKC isn’t set — “We don’t make promises on minutes; we don’t make promises on roles; we make promises on environments,” team president Sam Presti said Saturday — but such a financial commitment doesn’t happen without plans for playing time.

OKC won 57 games last season — the most in the West — and its championship window became wide open with big contracts this summer.

“I was in a situation where I love my teammates in New York. I really appreciate what Thibs and Leon [Rose, Knicks president,] did for me. And the fans in New York showed a lot of love,” he said. “But going into this situation is very exciting. From afar, I always saw how the culture was. The style of play really fits me. I’m a high-IQ player. There’s a lot of guys cutting. I think I’m one of the best passers in the NBA. And then just the culture, very family-based. It was just something that was really exciting for me. I feel like I can really expand my game.”

Losing Hartenstein put the Knicks in a bind as they navigate a diminished center market for a replacement. Logic indicates Thibodeau will start Mitchell Robinson, who is injury prone but was on an All-Defense trajectory last season before undergoing ankle surgery. They can still re-sign Precious Achiuwa using his Bird Rights, but sources said Thibodeau prefers him at power forward over center.

Centers Jericho Sims and second-round rookie Ariel Hukporti are also on the roster. League executives expressed skepticism that the Knicks, having depleted their asset chest in the Mikal Bridges trade, can swing a reported deal for Utah center Walker Kessler.

Charlotte’s Nick Richards is also a rumored trade target. Remaining centers in free agency include Daniel Theis, Cody Zeller, Tristan Thompson, Mike Muscala, Omer Yurtseven and Taj Gibson.

Hartenstein, meanwhile, is officially with the Thunder and hopeful about his “expanded” offensive role.

“You have to acknowledge the fact that Isaiah was coming from a great situation,” Presti said of his pitch to the player. “The worst thing you can do is to walk into a situation and try to diminish the current place that the player has played in. I think showing a lot of respect for that, respecting how difficult a decision can be like that for a player. Especially when they’ve had success, both personal and collective. You can always put your best foot forward.

“I think it’s less about thinking about the past with the other team and more about thinking about the future with your team. What that can potentially look like. Part of that with him being only 26 and our belief that we can continue his development and put him into situations where he can expand his strengths and what he does well. But these are really tough decisions for free agents. … Fortunately for us, I think he was able to see some of the things we were talking about.”

Jalen Brunson is eligible to sign his extension Friday, and if he does (it’s something he had been certainly considering during the season, according to a source), he’d be leaving quite a lot of money on the table.

The max extension Brunson can ink this summer is four years, $156.5 million. If he waits until free agency in 2025, he’s eligible for a new contract from the Knicks worth around $260 million-$270 million over five years.

Perhaps relevant to this conversation was Brunson’s reaction to OG Anunoby’s signing his five-year, $212 million deal. The point guard was blown away by the money.

“I said, ‘Damn.’ I was like what the eff. … $212 million?” Brunson said on his podcast, “Roommates Show.”

Does Anunoby’s getting that contract make it more or less likely Brunson agrees to an extension? I don’t know. But as the team’s best player, Brunson would be well below Anunoby in terms of annual and total salary.

There’s a world where signing this summer gets Brunson more money over time, however, since he’d be eligible for a second max extension sooner. Regardless if Brunson signs this summer or next, there’s no question he loves playing for the Knicks and has every reason to. He’s surrounded by friends and family, and every day is a college reunion.

The Knicks aren’t hiding from their mission. It’s a refreshing attitude after so many years of rebuilding and low bars.

“We’re all chasing Boston. We have to,” Brunson said. “They won at an elite level the way they played. So we got to figure out, without being on the court right now, how can we beat them? And that’s in the hands of the front office. And then when the season starts, it’s in our hands.”