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Assistant coaches Rene Meulensteen and Tony Vidmar will be tasked with getting Australia ready for the must-win match with Arnold forced to isolate.
The 58-year-old Arnold could yet be on the touchline for the fixture with his isolation period to end on the day of the match but will have to fulfill additional medical criteria to do so.
Socceroos defender Milos Degenek knows first-hand about the chaos a positive COVID-19 test can cause, having missed October's games against Oman and Japan due to the virus.
With most of Australia's qualifying campaign having been held during the pandemic, the centre-back has no doubt he and his teammates won't lose focus in the lead-up to must-win games against the Vietnamese and then Oman in Muscat on February 1.
"It's not a shock I guess, in the circumstances that we're living in where I think every third or fourth person is positive," Degenek said.
"Obviously it's not ideal for us but we know that Arnie's going to be here with us digitally in all the meetings and that... he'll be around.
"We're going to miss him because he's a head coach but with the staff that we've got - Rene, Viddy, JC (John Crawley, goalkeeping coach) and Clarkey (head of sports science Andrew Clark) - we've been together for last three or four years.
"Everyone knows what to expect and we know how to perform and all the messages are all the same."
Degenek was one of the first players to arrive in camp for the game against Vietnam as Australia attempt to end a three-game winless run as the road to Qatar enters its final stages.
Defeat to Japan and draws with Saudi Arabia and China dropped Australia to third in Group B with four matches to play.
Only the top two in the group will qualify directly for the World Cup with the third-placed team to face a tricky play-off route to the finals.
With the final two matches in March against Japan and group leaders Saudi Arabia, Degenek knows there's no margin for error in the next two games.
"We're all positive. We all know what's expected of us," he said.
"As Arnie said, you win the next four games you qualify for the World Cup and you leave nothing to chance.
"The best part about it is it's all in our hands. No one else can decide our destiny apart from us.
"We need to win. We need to play well. There are no ifs and buts about it."
