“Jalen would go over to the Bulls facility and practice with the Bulls players,” Pat Ambrose, Brunson’s coach at Adlai Stevenson High School who remains close to him, told The Post in a phone interview. “That’s where he became good friends with Derrick Rose. So your story gets deep with the Knicks. Derrick saw that young Jalen was a very, very good player and Derrick was a Chicago kid, and really started to mentor Jalen basketball-wise.”