Mayer was appointed in October 2015, overseeing the club’s history-making Championship and Premiership double of the A-League 2016/17 campaign. 

In what he has described as “the most gratifying role” of his career, Mayer said:

“This was a difficult decision for me to make because I have loved every minute of my time here at Adelaide United. 

“I want to thank the club’s board and sponsors, the club’s devoted members, the Red Army, and all Adelaide United fans for their unwavering support during my time here and I’ll be forever thankful for the opportunity they gave to me in this wonderful sporting code. 

“This was the most gratifying role of my career to date and the greatest highlight I’ve experienced would have to be the opportunity to host and win the A-League Grand Final in South Australia and at the Adelaide Oval. 

“I will remain in South Australia in my next role as CEO of the South Australian Jockey club, but I will continue to be an avid fan of this club and this sport in Australia.” 

Adelaide United Chairman Greg Griffin said he was disappointed to be losing someone so instrumental in the club’s recent successes, but thanked Mayer for his invaluable contribution over the last two years. 

“On behalf of Adelaide United’s board, sponsors, coaches, players, staff, and fans I want to thank Grant for his leadership and hard work from the moment he accepted the role with the club as chief executive officer. 

“I am, of course, disappointed to see Grant leave our club, but understand his ambitions and respect his decision. 

“We will begin the process of looking for a suitable and experienced replacement for Grant, but I am positive the current management team at the club will continue to lead us in the right direction. 

“Grant’s knowledge of sporting administration and the nature of sport in this country is outstanding and it is for this reason that we have appointed Grant an advisory board member of Adelaide United.”

Mayer will conclude his time at Adelaide United on Wednesday, 27 September.