Geelong's GMHBA Stadium will play host to the unlikeliest of A-League season openers.

After an increase in NSW coronavirus cases scuppered Western Sydney's plans for a bumper day of football, Western United's Monday night clash with Adelaide United has suddenly been bumped to the top of the run sheet.

The original plan was a much different one.

The A-League and W-League were scheduled to kick off in a double-header at Bankwest Stadium on Sunday with Western Sydney's A-League team to face newcomers Macarthur FC.

After coronavirus forced last season to be played in a hub, the new A-League season was due to become one of the biggest beneficiaries of NSW's plan to allow a return to full-capacity crowds.

Then the northern beaches cluster emerged.

First, the A-League announced any fixtures affected by border closures such as the grand final rematch between Sydney FC and Melbourne City would be postponed.

The league reshuffled fixtures, scheduling games between the six teams based in NSW and seemingly keeping the A-League opener on track while matching interstate teams against each other.

Then, on Wednesday, the double-header planned for December 27 was pushed back by three days, with permitted crowd capacity in NSW reduced to 50 per cent.

As a result, the season will open with 2019-20 semi-finalists Western United playing out of one of their temporary home grounds and hosting last season's seventh-placed finishers Adelaide in front of what is likely to be a small crowd.

Adelaide coach Carl Veart wasn't concerned about any extra pressure but admitted it would be strange featuring first-up.

"Normally when you get to see the first game you can judge to see where your team is," Veart said on Sunday.

"We're going in first game, not seeing any other teams playing. It's going to be interesting to see how we adapt."

Despite the fixture changes, the A-League's opening week still shapes as a hectic one.

Brisbane Roar will host Melbourne City on Tuesday, while the rescheduled Wanderers-Bulls clash will take place on Wednesday, and Central Coast and Newcastle will face off in a New Year's Eve derby.

Reigning champions Sydney FC kick off their title defence against Wellington on January 2, with Melbourne Victory to play Brisbane later that day.

On Sunday, Macarthur will play their first home game at Campbelltown Stadium against the Mariners, with Adelaide to host City in the final game of the week.

Perth Glory are the only team who won't feature with their season opener not until January 16.