Maxwell Chapman, 37, of Albany, Western Australia, had been in Melbourne just a day before he was elbowed viciously in the head outside Showgirls Bar 20 in King Street after an argument with two men.
He fell and hit his head on the footpath, suffering serious brain injury.
The man's father, Victor, said: ''For goodness sake, hand yourself in. I'm feeling numb at the moment because I just don't know what is around the corner. Doctors won't know anything now until they bring him out of the coma.''
Mr Chapman said doctors at The Alfred could not say whether his son would fully recover but had operated to staunch bleeding in his brain.
He said his son had arrived in Melbourne a day before the attack because he was planning to move here and had come to find a house.
Constable Steven Hemingway said no one had tried to stop the offender but the club's security guard had given first aid to the victim, who lay on the ground as the attacker walked away.