The Jets' round-six A-League game on Boxing Day at McDonald Jones Stadium was called off on Christmas Day after the Wanderers' infections grew.

One positive case among the Wanderers group was announced on Thursday but the Newcastle Herald understands that number grew to five by Christmas Day, leading to the postponement.

It is understood four or more losses due to COVID-19 in any club's group - including players and football staff - can trigger a postponement.

Newcastle were set to be without key starters Angus Thurgate and Jordan Elsey because of the virus. However, Thurgate was regaining fitness after coming out of isolation during the week following his infection, which forced the midfielder to miss the previous Sunday's 2-1 loss to a 10-man Macarthur. Reserve goalkeeper Noah James was in the same situation.

Elsey was a late withdrawal from the defeat to Macarthur at Campbelltown Stadium because of a positive test to COVID-19.

The Herald, though, understands that the centre-back, like Thurgate, is asymptomatic, meaning he also returns from isolation well inside the 14-day period which was in place under former rules.

Changes to the regulations mean asymptomatic cases can be back training and playing earlier, giving the pair an outside chance to be fit and available for Newcastle's next game, at home against City on Saturday.

That clash remains in doubt because of City's COVID-19 issues after their FFA Cup match against Wellington Phoenix last week and Monday's A-League game against Brisbane Roar were postponed because of six positive cases in their playing group.

But again, if their affected players are asymptomatic, the match with Newcastle could go ahead as scheduled.

The Jets were sixth on five points from five games ahead of other matches on Sunday night.

AAP reports: Western United coach John Aloisi hoped his club had contained its COVID-19 breakout, while Melbourne Victory mentor Tony Popovic believed it was just a matter of time before everyone tests positive to the virus.

Three Western United players were ruled out of last week's 1-0 win over Adelaide United, and those same three players missed Sunday's A-League clash with Melbourne Victory at AAMI Park.

Nine clubs have been hit with COVID cases in recent weeks, but Aloisi said the virus hasn't spread beyond the initial three players at Western.

However, he is well aware that situation could change in the blink of an eye.

"Look, you can never be on top of it, because I don't think the country is on top of it," Aloisi said.

"But we're on top of it as much as we possibly can."

Victory played against Melbourne City last week, and players have been nervously waiting to see if they were exposed to the virus during the game.

"I think everyone is a little bit nervous about what's happening and what could happen next in this situation," Popovic said. "But look, we've done what we had to do in terms of our testing and precautions. We're doing our best as a football club in alleviating any anxiety."

With athletes from all around the world now testing positive to the virus, Popovic is adopting the attitude of when, not if.