THE HIGHLY anticipated 'full-house' derby between Fremantle and West Coast has suffered a cruel blow with the West Australian government changing its mind on COVID-19 restrictions.

The easing of restrictions is on hold which means stadium attendance will be capped at 50 per cent, and the once expected crowd of 60,000 will be slashed to 30,000.

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WA premier Mark McGowan said on Friday that the decision was based on the latest advice from the state's chief health officer to protect the people of Western Australia.

Initially planned to be introduced on Saturday, July 18, the new proposed date for the introduction of the more relaxed 'phase five' restrictions has been moved to Saturday, August 1.

"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," Mr McGowan said.

"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 proportions to protect our citizens."

Mr McGowan listed hotel quarantine numbers and the worsening situation in Victoria as key reasons for the delay.

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

"As a result, our chief health officer has recommended a delay in the introduction of phase five. 

"We've decided to be extra cautious here. I wish we could move to the next phase … but a slight delay is a responsible and sensible decision to make."