Shaquille O’Neal says Phil Jackson meant well, but his cardinal sin during his three-year, three-month stint as Knicks president was trusting that millennial NBA players would adapt to the selfless aspects of the triangle.

In a conference call promoting TNT’s coverage, O’Neal supported Jackson’s attempt at resurrecting the Knicks while Charles Barkley said he got “a bad rap’’ and partner Kenny Smith believes he erred by not taking over the bench.

The post-Jackson era begins Thursday in Oklahoma City with a new, high-tempo offense and new management team willing to de-emphasize making the playoffs for this one season in order to gain another high lottery pick.

“I think Phil went wrong in believing the mindset of these players would believe in him and his system for the triangle,’’ said O’Neal, who won three titles with Jackson with the Lakers. “I’ve said many times, the triangle worked. Guys have always tried to debate it as: Of course it worked with Shaq and Kobe and Mike and Scottie but Carmelo [Anthony] got [Kristaps] Porzingis and some role players. I think if they would’ve bought into the system, it would’ve been much different. But they never bought into the system.’’

Smith, the Queens native, wished Jackson could have taken the coaching reins when things unraveled. (Jackson had health issues.)

“As general manager, he didn’t have the same levity as a coach,’’ Smith said. “As a coach, you’re in the trenches and in the moment and you can help make decisions and help people through it. As general manager, he was making the same actions, comments and movements as if he was there every day. If he was there every day, I wanted him to coach. I think he should’ve come down and coached the team. Nobody knows the system like he does. Nobody knows the structure of a team like he does.’’

Barkley said Jackson “got a bad rap,” still touting the acquisitions last offseason of Derrick Rose and Joakim Noah as a gamble worth taking.

“We did this conference call last year, were excited about Derrick Rose and Joakim Noah,’’ Barkley said. “I thought the Knicks would be really good. Neither worked out — plain and simple. He rolled the dice.’’

Meanwhile, O’Neal is skeptical Anthony will be the difference-maker in OKC because of his trait of “the ball sticking.’’

“I think at this point of Carmelo’s career if he wants to win, he should look at teams like Golden State and San Antonio that move the ball,’’ O’Neal said. “[OKC] can make a lot of noise if things are done the right way.’’

O’Neal commended Anthony for waiving his no-trade clause to live in the NBA’s smallest market.

“He realized, do I still want to get mine or do I want to win? Do I want to be remembered as a winner or guy who put up big numbers?” Shaq said.

Knicks rookie point guard Frank Ntilikina returned to a contact scrimmage for the first time since bruising his right knee in the preseason opener Oct. 3. Ntilikina is expected to come off the bench to spell Ramon Sessions in the opener.

“He did good,’’ Jeff Hornacek said. “He’s going to pick guys up, use his length. He got us into the offense, cutting hard and learning the little things about his teammates every day — where they like the ball. He’s a solid right now. We don’t have any fear of having to put him in the game.’’