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Arnold was a high-profile absentee during Australia’s 4-0 qualifying win against Vietnam at AAMI Park in Melbourne after he was forced into isolation following a positive test for Covid-19.
The 58-year-old was cleared on Friday after his week in isolation to join the Socceroos for their flight to Muscat ahead of Wednesday’s (AEDT) match.
After a week of forced remote coaching and missing the Vietnam match, The three-time A-League coach of the year admitted he was relieved he could get back to the sideline.
"That (Thursday’s match against Vietnam) was probably one of the worst nights of my life, to be honest. It was really hard," Arnold said.
"It's hard enough standing on the bench and watching a game or sitting up in the grandstand watching a game but to watch it on a computer connected to the bench with headphones ... with the delayed coverage - it was about a minute later than what was going on at the ground - that made it a little bit harder but the communication was there.
"I'm just so grateful to the great staff that I've got and there's one thing I probably have learnt more out of this than ever is trust is the key.
"You need to trust people especially in the staff that you have but also the players. They handled the challenges very well."
For the Oman match, the Socceroos will also welcome back suspended midfielder Ajdin Hrustic and defender Aziz Behich, who was unable to fly to Australia due to a blizzard in Turkey.
Australia's win over the last-placed Vietnamese was important with rivals Japan and group leaders Saudi Arabia also winning their latest qualifier.
Japan defeated China 2-0 to stay one point clear of the third-placed Socceroos before facing the Saudis in a huge match for all three nations in Saitama on Tuesday.
Thursday's victory, which featured debuts for Josh King and Marco Tilio, was secured with goals to Jamie Maclaren, Tom Rogic, Craig Goodwin and Riley McGree.
"It was nerve-wracking," Arnold said.
"It was a good performance but second half we were a bit sloppy and we're now stepping up against better opposition and we need to get rid of that."
