It was an extraordinary week for Doncic, who led Real Madrid to a Liga ACB championship on Tuesday. He was in New York by 9 p.m. Wednesday, and jet lag took hold a few hours later. He awoke at 4 a.m., he said, and resigned himself to playing video games in his hotel room. He also knew that Thursday would be seismic.

Sure enough, after the Atlanta Hawks selected him with the third overall pick, Doncic walked across the Barclays stage at 7:47 p.m. to shake hands with Commissioner Adam Silver. Doncic soon learned from his agent that the Mavericks were trading for his rights, but the deal was not official when he began to make the rounds for interviews with ESPN and NBA TV, and one for an in-house crew, which was aired live on the jumbotrons.

Doncic did all of these under the guise of still being a member of the Hawks — he was very excited — and it looked all the more official because he was still wearing the team’s hat.

But after ducking into a lounge area for a private call with officials from Dallas, Doncic emerged a few minutes later with a new (Mavericks) hat. He handed his old (Hawks) hat to a staffer from the N.B.A., and asked her if he could hang onto it as a keepsake. She assured him he could do whatever he wanted: It was his night.

As all this was playing out, Slavko Baranja, a New York-based photographer with the Slovenian Press Agency, waited patiently in a nearby corridor. He carried an oversize Slovenian flag. Baranja was, in that moment, an ambassador for everyone back home in Slovenia — population: 2.1 million — who wanted to wish Doncic well.