The unnamed Jets player is believed to be the first professional footballer in Australia to test positive to the virus.

Newcastle's club doctor told Topor-Stanley and his teammates to self-isolate on Friday night when the player's positive test result came back.

But NSW Health said that was unnecessary on Saturday and the Jets players returned to following social-distancing protocols instead - unless they start to show symptoms.

Melbourne City were notified having played Newcastle on Monday night before the A-League was postponed until April 22. The match officials have also been notified.

The player didn't have any symptoms and only found out he had the virus after being tested so he could travel overseas.

A member of the Wellington Phoenix coaching staff has reportedly also caught the virus following their stay in Sydney in an attempt to complete the season.

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While unable to reveal the player who tested positive, Newcastle chief executive Lawrie McKinna confirmed to The Canberra Times it wasn't Topor-Stanley.

The 35-year-old has been with the Jets since 2017 in his second stint with the club.

"We isolated everybody [Friday] night and later on [Saturday] we got all the medical advice back ... and it said everybody's fine," McKinna said.

"I can't tell you who the player is, but I can assure you it's not the big fella [Topor-Stanley]."

The Jets also notified the Newcastle University, where they train, as well as the Newcastle Stadium, so the proper cleaning precautions could be taken.

They introduced protocols three weeks ago to help minimise the chance of infection spreading throughout the club.

But McKinna said it was reminder of how important it was to take precautions.

"We have notified all the players again that we have to be careful because it's serious," he said.

"Don't think we're indestructible because that's proven that we're not indestructible. The boys are off on their own training programs at the moment with the league suspended until April 22.

"Everybody will be home and hopefully just going out when they need to go out."

Football Federation Australia said they would support the Jets.

"The health and wellbeing of players and officials continues to remain FFA's highest priority at this difficult time," an FFA spokesperson said.

"FFA is working with the club to ensure that they receive they support they require."