A few years ago, LeBron James, as he does from time to time, lauded the accomplishments of a friend’s child on social media. That friend was Damon Jones, whose daughter had made the second-team all-district team for her high school basketball play.

“Yeeeaahhhhhhh niece!!! Congratulations!! First Team coming next!!!” Mr. James wrote.

It was one of many signs of the superstar’s friendship with Mr. Jones, to whom he has been close ever since they played together on the Cleveland Cavaliers from 2005 to 2008. Mr. Jones, a backup guard who started 10 games over those three seasons, has traveled the world with Mr. James and gotten jobs because of his connection to Mr. James, including as his personal shooting coach. According to federal prosecutors, that wasn’t the only way Mr. Jones may have benefited from his relationship with basketball’s biggest star.

On Thursday, federal officials announced that Mr. Jones had been indicted for his role in a sports gambling ring, and separately for his role in rigged poker games that involved Mafia members. The indictment said Mr. Jones used his friendship with an unnamed player (who matched the description of Mr. James), and his proximity to the N.B.A., to sell insider information to gamblers who then placed bets based on that information.

Mr. James has not been accused of wrongdoing.

Being friends with a professional athlete, especially as part of their entourage, has long been a kind of social currency. Beyond dates and V.I.P. access, it can open up networking opportunities with the rich and famous, and sometimes provide a fast track into careers that are otherwise difficult to break into.

And because of that, players are often warned about the dangers of letting the wrong people into their circles.

There are tales of family members stealing money from professional athletes, of friends using an athlete’s fame for personal gain. It is a phenomenon as old as professional sports.

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