But McLachlan, who is the League's deputy CEO, will have to survive an executive search process if he's to win the top job.
And a star-studded field is expected to contend for the position, with Channel Nine and AFL veteran Jeff Browne, Collingwood president Eddie McGuire, AFL commissioner and Seek founder Paul Bassat, Geelong chief executive Brian Cook, West Coast CEO Trevor Nisbett and Melbourne Cricket Club boss Stephen Gough among the early names being mentioned.
Indeed, McLachlan's task of gaining the position has been made harder by the fact that Demetriou will not play any role in the appointment of his successor.
"Andrew and I have been discussing transition since 2012," AFL chairman Mike Fitzpatrick told the press conference at which Demetriou announced his departure.
"The CEO's job of the AFL is very complex and it's a very demanding job. It's good management to start talking about these changes as early as possible, which we did.
"The AFL Commission has retained an executive search firm to assist the AFL Commission to identify potential candidates to succeed Andrew as chief executive officer.
"Our aim is to complete the process as soon as possible, but our first priority is to identify the best person for the job.
"Andrew will remain with the AFL until the end of the season, but will have no role in identifying or selecting his successor, in line with good governance."
As for whether his successor needs to be a "football person", Demetriou said: "It's a very complex business, the AFL and the industry. It has changed in so many ways.
"I think if you've got a knowledge of the football industry it is certainly an advantage. I think it's difficult for someone who hasn't got football experience.
"But it's not a prerequisite or a non-negotiable."
Demetriou has emphatically ruled out seeking a career in politics after he finishes with the AFL.
But he has been tipped to join James Packer's burgeoning gambling empire, as a board member of Crown Resorts Limited, when he finishes with the AFL.
"I really have no interest in (working in) another sport, to be honest," Demetriou said. "This is the sport.
"You've got to be asked to join a board. If I'm asked, I'll look at it in good faith. I've got a lot of respect for James Packer and the Crown company.
"But you've got to be asked, so we'll wait and see."