The western derby was set to become a 60,000-seat sellout after the Western Australian state government announced it would further ease coronavirus restrictions on July 18 - the day before the game.

But those plans have since been scrapped due to the worsening situation in Victoria.

It means WA will remain in phase four of restrictions - allowing only half the stadium to be full.

It's believed about 40,000 tickets had already been sold before ticket sales were put on hold earlier this week.

It means about 10,000 people who already bought tickets will no longer be able to attend, given the capacity will now be capped at 30,000.

Fremantle, who are the home team, are yet to announce how they plan to allocate tickets for the match.

"As I said when we first announced phase five, we would only introduce it under the watchful eye of our health experts," WA premier Mark McGowan said.

"Today we were provided with the latest health advice and that health advice is clear.

"Given the number of people in hotel quarantine and the situation in Victoria worsening, there is an increased risk of the virus spreading (here in WA).

"I realise it won't be popular with some people and I understand in particular with the Eagles/Dockers game there will be some problems.

"It will have to be managed by the football clubs and we will work with them to manage it as best as they can.

"This is a small price to pay to put in place precautions to protect our citizens."

Australian Associated Press