Frenzy became bedlam on the next play. Flagg talked trash to James, ran to his spot on the left wing, pivoted off the catch and nailed the shot before turning to exult with his future Mavericks varsity teammates, who cheered him on decked out in casual wear from their courtside seats.

Cooper Flagg strolled into UNLV’s Thomas and Mack Center at 4:17 p.m. for his Summer League debut, wearing Dallas Mavericks gear, bright white New Balance shoes, and an emotionless look on his face as he passed through security.

Cooper Flagg called his NBA Summer League debut “one of the worst games of my life” after shooting 5-of-21 from the field.