APA Group's long-standing chief executive Mick McCormack will head for the exit door next year after 14 years in the role, with the decision to retire coming less than a month since the $13 billion takeover bid for the gas pipeline owner by Hong Kong-based suitor CK Group was blocked.

The move, while not totally unexpected, leaves big shoes to fill at the head of the country's biggest transporter of gas, with internal candidates to be matched up against external ones for the the role.