ATHENS, Greece—After three excruciating overtimes and the most epic game of his life, the 18-year-old kid bound for NBA superstardom was broken. He couldn’t bear to look at the scouts in the courtside seats. Or the riot police on the baseline. Or the mob of fans lighting flares inside a dingy gym.

Filathlitikos, the only pro basketball team that Giannis Antetokounmpo had ever known, was about to lose its unlikely shot at promotion from the second division of Greek basketball in 2013. As red smoke filled the gym, Antetokounmpo sobbed into his jersey.

Christos Petrodimopoulos, a 7-foot center nearly twice his age for opposing Kifisia, had almost single-handedly crushed Antetokounmpo’s dreams. Petrodimopoulos spotted Antetokounmpo sitting on the bench and cleared a path through hundreds of fans and cops to put his arm around Antetokounmpo.

“You’re very young,” he told him. “Don’t cry. You have a future.”

Antetokounmpo was so devastated that he couldn’t look up to see who was consoling him. He would have been staring at a man who now owns two successful Coffee Island franchises here.