ProServ expanded into basketball, and Dell signed Patrick Ewing, Michael Jordan,[2] and other top NBA players.

Donald has a younger brother, Dick, who worked at ProServ and went to the University of Michigan and was Big Ten Tennis Champion.

He was also a founder of the ATP Players' Union with Jack Kramer and Cliff Drysdale in 1972, and he was co-founder with John A. Harris, head of Potomac Ventures, of the Citi Open tennis tournament in Washington, D.C. in 1969.

[4] Dell is the vice chairman of the International Tennis Hall of Fame and a member of the board of directors for the Arthur Ashe Institute of Urban Health.

Dell was a tennis commentator for PBS and NBC television in the 1970s and 1980s with Bud Collins and Barry MacKay, and he made appearances on WUSA, the CBS local affiliate station.