That contact is about to become more frequent. McGrady and O’Neal, who have 13 N.B.A. All-Star appearances between them, said in a phone interview that they plan to open a player representation agency this fall. They will call it Seven1 Sports Group and Entertainment. The name is a mash-up of their jersey numbers from careers that propelled McGrady to induction into the Basketball Hall of Fame in 2017 and enabled O’Neal to play for seven teams across 18 seasons and sign player contracts worth more than $150 million. If successful, they would become the most prominent players in N.B.A. history to enter the highly competitive and hard-to-break-into agent business.