Among his most prominent work as a sports industry attorney, Greenberg was instrumental in a deal that landed NHL Hall of Famer, Mario Lemieux,[3] ownership of the then-bankrupt Pittsburgh Penguins hockey team in 1999.
He is credited with helping the organization set fan attendance records,[7] while continually re-investing money to improve the Blair County Ballpark, which resulted in national recognition of the franchise as one of the most innovative teams in professional sports.
Greenberg worked with the university to create the area's first-ever professional sports franchise, the State College Spikes, which began play in the New York-Penn League in 2006.
[14] Greenberg took over as president and managing partner of the Myrtle Beach Pelicans in June 2006 when he and a group of investors purchased the Minor League Baseball team.
[15] Greenberg worked to enhance TicketReturn.Com Field in Myrtle Beach, making it one of the most fan-friendly venues in Minor League Baseball.
As part of a stadium redesign, the franchise moved the visitor's bullpen from beyond left field to beside a dugout, and set up 500-seat bleachers in its place.
[21] In August 2014, Greenberg, along with Scott Sonju, led an ownership that purchased the Frisco RoughRiders, the Double-A affiliate of the Texas Rangers.
[22] The new ownership group has spearheaded numerous major franchise improvements, from a completely new team identity to massive additions and upgrades to Dr Pepper Ballpark, including a giant new 2,763-square-foot HD video board and nearly 2,500-square-feet of new or upgraded LED boards, a new state-of-the-art sound system, a newly designed and modernistic video control room, an open-air in-park sports bar, a relocated and expanded team store, known as "Riders Outpost", improved food service and menu, and a complete overhaul of in-game entertainment.
[26] The Dallas Observer said in April 2010 that Greenberg "has the money and moxie to lead the Texas Rangers back to relevancy and into the playoffs.
"[27] Greenberg served as managing partner and CEO of the Rangers, while Ryan continued in his role as team president.
Greenberg's vision for the team included both a dedication to being the best at every aspect of the operation and a focus on creating a highly entertaining fan experience at the ballpark.
"[28] Rangers General Manager Jon Daniels has praised Greenberg for his personal connection to the fans, noting "He's just a normal guy.
"[27] During the 2010 World Series Greenberg, as a guest on a local ESPN radio show, Ben and Skin, made negative comments about the New York Yankees fans during the ALCS.
[31][32] Club president Nolan Ryan assumed the title of CEO, overseeing all aspects of the Rangers operations on both the baseball and the business side.
[31][32] In July 2017, Greenberg was reported to have signed a letter of intent to purchase the Carolina Hurricanes NHL franchise for approximately $500M.