Greg was the Chairman of Adelaide United FC from 20 November 2010 when a syndicate of which he was the major shareholder purchased the Club. With the sale of the Club to overseas interests in March 2018 Greg was appointed as Legal Counsel to the Australian Professional Football Clubs Association (APFCA) and has been part of the FIFA/AFC mandated body, the Congress Review Working Group in 2018 and the FFA Congress mandated body, the New Leagues Working Group in 2019 which is working on the framework and legal issues for an independent A- League to be separated from the FFA and owned and run by the 12 Australian A- League Clubs.