James Stannard's coach feared the veteran rugby sevens playmaker had been killed when his head smashed into the pavement in a one-punch attack on Good Friday.
Reliving the frightening early-morning incident, an emotional Andy Friend revealed there was no warning before the incident that left Stannard with a fractured skull outside a Coogee kebab shop.
A 22-year-old British man has been charged over the blow.
Friend said he was standing near Stannard and saw his head hit the pavement "very hard".
"My instinct was that it wasn't good, that it was fatal," he said on Saturday.
Friend's next instinct was to make sure the fleeing perpetrator didn't get away, helping to detain him for police with help from star players Lewis Holland and Ben O'Donnell.
Despite initial fears, Stannard has been told by surgeons he's likely make a full recovery and is free to leave Sydney's St Vincent's Hospital.
In an emotional press conference, Friend revealed the 35-year-old had been cleared by his neurosurgeon and an ear, nose and throat specialist.
However, he said Stannard was likely to wait until Sunday to return home.
"He's doing really well. It didn't look good, but he's doing really well," a relieved Friend said.
The blow brought back terrible memories for Friend who was the Brumbies coach in 2009 when Shawn Mackay died from head injuries sustained in a road accident in South Africa.
"It was one of those surreal moments where the world stops," he said. "Sadly I've seen that situation before.
"What staggers me is we can get to the stage where we feel we can act with such violence to an individual."
Friend said his family, Stannard and other rugby sevens players and staff had surprised him with an early farewell party, as the Commonwealth Games will be his last event as coach.
The coach said it was a special night and nobody wanted it to end - and the violent way it did end had come "out of the blue".
"All I know was there wasn't an ounce of aggression all night, it was a beautiful night," he said.
"I can assure you it was not a boozy affair that was going to turn sour."
Without Stannard and incumbent captain Holland, Australia enter the Gold Coast Games without an experienced leader as well as their best two playmakers.
It leaves their medal hopes all-but shot, but Friend was quick to point out his young side thrives under adversity.
"One thing I now about this team is there's tremendous character, there's tremendous belief and every time we've had one of those occasions ... we step up and take it to another level," he said.
Friend has called Brandon Quinn into his 12-man squad for the Games tournament but is yet to decide on his new captain, with Tom Lucas and Jesse Parahi the prime candidates.