LAS VEGAS — Organizers of the N.B.A.’s summer league here have traditionally closed the upper deck of the Thomas and Mack Center by draping black curtains to cover rows of empty seats. While attendance and interest have grown in recent years, the summer league, an off-season showcase, is still a niche event, aimed at die-hards who want a first look at young prospects.
But with Lonzo Ball, the second overall pick in the recent N.B.A. draft, and the Los Angeles Lakers headlining on Saturday, the league had to stop selling tickets on Friday because of overwhelming demand, the first time the event has sold out in advance.