He played in the National Basketball Association (NBA) for the Buffalo Braves, Los Angeles Lakers, and Boston Celtics from 1973 to 1978.

Due to a severe knee injury suffered early in DiGregorio's professional career, he played only five NBA seasons.

[1] At age 12, he decided to become a professional basketball player, and put in thousands of hours over the years to develop his skills.

[2] They eventually lost to Memphis State,[6] but only after Barnes sustained a knee injury that forced an early exit, after playing only 11 minutes in the game.

[8][9][12] Providence retired his number at halftime of a February 5, 2008 game against DePaul, giving the fans DiGregorio bobblehead figures.

[13] Among others, the U.S. team also included future Hall of Fame center Bill Walton,[14] Swen Nater (who replaced Walton after an injury in game 1), Providence teammate Marvin Barnes, future Hall of Fame player Bobby Jones,[15] Pat McFarland, and Tom Henderson, who defeated the Soviet team in the bruising six-game exhibition series,[16][17] which helped heal the still-open wound of the United States' loss in the 1972 Summer Olympic finals.

He was selected third overall by the Buffalo Braves (a franchise now known as the Los Angeles Clippers) in the 1973 NBA draft, out of Providence College.

[25] In 1977, he joined fellow NBA stars Julius Erving, Rick Barry, Wilt Chamberlain, and Pete Maravich,[citation needed] in endorsing Spalding's line of rubber basketballs, with a signature "Ernie D." ball making up part of the collection.

[26][10] Before the 1977–78 season, the Brave's sold DiGregorio's contract rights to the Los Angeles Lakers, after Buffalo had acquired future Hall of Fame point guard Nate "Tiny" Archibald; part of a greater plan of player transactions in Buffalo.

[21] He was also a referee in the Continental Basketball Association for a year, and worked with an advertising firm in public relations.