Witnesses heard a loud thud as Sydney man Simon Cramp dropped to the ground on a late-night strip and his head "bounced" on the concrete.
Moments before Mr Cramp was punched and lost consciousness on Sydney's George St, Daniel Angelos was allegedly seen making a "beeline" for him.
Angelos, 24, is on trial in Downing Centre District Court after pleading not guilty to intentionally causing Mr Cramp grievous bodily harm in the early hours of June 3, last year.
He has pleaded guilty to a lesser assault charge.
The first day of the trial heard on Monday that Mr Cramp and two friends had left The Argyle at The Rocks and were walking down George St when the assault happened.
Crown prosecutor Sara Bowers told the jury they would hear from Mr Cramp's friend, Mitchell Gardiner, who saw a man looking aggressive and swearing.
Ms Bowers said as the man got closer he said "What are you looking at?"
The man made a "beeline" for Mr Cramp and allegedly punched him with a closed fist, the court heard.
Angelos was later identified as the alleged attacker.
Mr Gardiner saw Mr Cramp lose consciousness and then fall backwards onto the concrete pavement.
He saw Mr Cramp's head "bounce" on the pavement, the court heard.
Another friend with Mr Cramp, Laura Symes, will give evidence she saw Mr Cramp punched "two or three times".
Ms Bowers said Ms Symes went to her friend's aid as he lay on the ground and noticed blood coming out of one of his ears.
Angelos's defence lawyer Brian Murray told the jury his client agreed he involved himself in causing Mr Cramp grievous bodily harm but that he only intended to cause actual bodily harm.
The court heard after the punch, Mr Cramp was taken to hospital for life saving treatment and to relieve pressure on his brain.
He made a remarkable recovery, Ms Bowers said.
The trial continues.
