FFA are currently considering a string of bids from expansion hopefuls to grow the 10-team league in time for the 2018-2019 season.

Should new sides be admitted then, it won't be a moment too soon for the national coach.

The 2015 Asian Cup winner, who is on record as supporting expansion, renewed his argument at a Melbourne Victory business function on Friday.

"Our participation rates are at record numbers and we've had less professional teams than we've ever had. It doesn't make sense," he said.

"If you speak to all our greatest players, the ones who played here first, and you ask when they first played in the NSL, it was at 17, 18, 19 years old. The reason was because we had 15 or 16 teams.

"You could show your ability and potential and grow and you'd get picked up by the big clubs or you'd go overseas.

"We're putting at risk future national teams (without expansion). The talent pool's too narrow, the opportunities are too narrow."

Postecoglou stressed he was speaking from a football perspective, and "there needs to be another discussion about the financials and where teams are going to be placed".

Melbourne Victory chairman Anthony Di Pietro was happy to speak to those issues.

In what could be read as a swipe at leading expansion prospects South Melbourne, which derives much of its support from Melbourne's Greek community, Di Pietro insisted new clubs must bring come with broad appeal.

"At the core of any expansion, we must be confident that any new licenses don't compromise the mainstream integrity and the marketability of the competition," he said.

"They must embrace all of us who enjoy sport. Far too much money has been invested in the A-League and we've got to learn from lessons past; both good and bad."

The Victory boss insisted his club was firmly in support of expansion amid wide-ranging change to the code.

"The time for engagement, decision and change is now upon us. Decisions to be made right now are going to affect the future of football in Australia for years to come," he said.