Simon Cramp remains in an induced coma in the intensive care unit of a Sydney hospital after he became innocently caught up in a brawl between two gangs of men in the Rocks.

His mother, Shellharbour businesswoman Angela Cramp, remains by her son's bedside.

Police believe Mr Cramp, 26, from Cremorne Point met with a classic "wrong place, wrong time" scenario, standing with two friends under the awning of a McDonald's restaurant around 3am on Sunday morning.

On any given Friday or Saturday night, that is peak hour for foot traffic in The Rocks. Taxi changeover hour means there are more people than cabs, tumbling out of the bars to look for a way home, or something to eat, the next pit stop, or trouble.

This weekend while the suburbs slept beneath a blanket of rain, one group of 10 and another of four were throwing punches at one another on the corner of Bridge and George streets.

Security guards and passers-by broke up the fight and groups dispersed.

The larger pack drifted south, but the smaller one reeled north and set upon an unrelated bystander, attacking him with such ferocity that he still fights for his life.

Police have taken statements from a number of witnesses, who said the injured man was not involved in the brawl and was an innocent bystander.

Detectives are examining CCTV of the brawl, including footage collected by some of the restaurants and bars in the Rocks. No arrests have been made.

Inspector Greg Jewiss from The Rocks local area command said the victim was repeatedly punched until he fell to the ground, hit his head and lost consciousness.

"The victim and his friends happened to be sitting there and witnessed the first incident," Inspector Jewiss said.

"There were words between the groups and unfortunately it's escalated from there."

The men who were involved in the earlier fight were believed to be the aggressors.

Paramedics stabilised the man at the scene and took him to St Vincent's Hospital for emergency surgery on his head. He remains in a critical condition.

Inspector Jewiss appealed for anybody who witnessed the fight to contact police.

"There's a lot of people at that location at that time in the morning," Inspector Jewiss said.

Another man who was involved in the first fight was also admitted to St Vincent's Hospital but discharged with minor injuries.

www.smh.com.au