And he became just as interested in the artists as in their work.

“Why do they do the things that they do?” he said. “Fascinated with the way they think. As I get more information from them, I gravitate closer and closer to them. That helps me understand a little more.”

After a job out of college working in e-commerce, St. Fleur decided to follow his passion. Villalongo introduced him to Peggy Cooper Cafritz, who had a prestigious African-American art collection, and she gave him an assignment: Help her find new artists who were finishing graduate school.

Not long afterward, he decided to push into the art business full time. And from there came his involvement in the N.B.A. ecosystem, a relationship built in part from the days when St. Fleur would hang around the Rucker Park and West Fourth Street basketball courts in Manhattan, meeting people who eventually became player agents. Getting to know Deron Williams, the former Nets guard, became fruitful, too. Williams was looking to build an art collection, not just acquire a few pieces.

So St. Fleur got involved, and soon his name began to hopscotch around the league.

He has worked with Houston Rockets forward P. J. Tucker, Hall of Famer Alonzo Mourning and Yankees pitcher C. C. Sabathia, among others, he said. Knicks guard Courtney Lee was connected with him through the team, St. Fleur said, after he had previously built a relationship with Carmelo Anthony, the former Knicks star. N.B.A. veteran Dahntay Jones started talking to St. Fleur about art while he was working out at Manhattan’s Sky gym last summer, where Anthony held his popular “Hoodie Melo” scrimmages.

In his work, St. Fleur has tried to be as much teacher as salesman. He introduces athletes to artists, trying to break through the intimidation that affects some players. St. Fleur sends out newsletters to enlighten players, ships books to display different artists and styles, and texts photos of works to players if he believes one or more of them might be interested. Sometimes, he’s there to caution a player against overpaying.

You don’t need millions to buy art, he often says.

When Jay-Z released his latest album, “4:44,” St. Fleur was flooded with text messages. A song, “The Story of O. J.,” with its references to buying artwork, had served as a jolt to some players, reinforcing what St. Fleur had been telling them for years: that art can also be an investment and a way for generations to create something to pass down.