Once Isaiah Hartenstein determined success with the Knicks was impossible the way he played, the 7-foot German-American center got blunt with the image in the mirror.

“I was in a situation where I played one way, but I looked at myself and was like, ‘You’re not playing good — be honest with yourself, it’s not working,’” Hartenstein told Post Sports+. “And then it was: How can I change it to help the team and how am I going to stay on the court?”

This revelation came to him last season, Hartenstein’s first with the Knicks. He was dealing with Achilles pain as well as the realization that the style of basketball he knew — along with the skills he had spent a lifetime developing — were largely frivolous for a center in Tom Thibodeau’s system.

The Knicks wanted a bruiser at that position. A screener. A rebounder. Similar to Mitchell Robinson.