In the Knicks’ season-opener Oct. 17 against Atlanta at Madison Square Garden, an audacious dunk over just about everyone on the court announced his arrival.

“We went crazy when he dunked that one,” said Golden State forward Kevin Durant, who was watching at home with friends. Durant knows Trier from his rookie season with the Seattle SuperSonics, before the franchise moved to Oklahoma City. “We’re so happy for Zo. We’ve seen Zo grow up. We had a little hand in raising him, a little hand. So it feels good for him to have this success. He’s a pure baller.”

Trier’s journey from middle school prospect to the pros is an allegory, for better or for worse, of these basketball times. After establishing himself as one of the best in A.A.U. basketball, he played for four different high schools, in Oklahoma City, Tulsa, Rockville, Md. and Las Vegas, the quintessential free agent in the world of elite high school basketball.

He was one of the most coveted recruits in the country and a finalist for the 2015 Naismith Boy’s High School Player of the Year before he signed with Arizona. Plans to be one-and-done and off to N.B.A. riches changed after he broke a bone in his shooting hand. The Pac-12 All-Freshman team selection returned for his sophomore year.