Melbourne Crime Investigation Unit detectives are investigating after an assault in the Melbourne CBD on 5 August.
Investigators have been told a 42-year-old man was standing with a friend outside a fast-food restaurant on Elizabeth Street when he got into a verbal altercation with an unknown man about 2.25am.
The offender has then punched the 42-year-old, causing him to fall to the ground, hit his head on the footpath and lose consciousness.
The victim was taken to hospital with significant head and neck injuries.
The offender left the scene on foot heading south towards Flinders Street.
Investigators have released images of a man they believe may be able to assist with their enquiries.
He is described as being in his 20s of thin build with olive skin. He has dark hair in dreadlocks or braids to his shoulders, a black beard and was wearing a dark coloured shirt and a black blazer with black jeans ripped at the knees and white casual shoes.
Anyone who witnessed the incident, recognises the man, or has information that can assist investigators is urged to contact Crime Stoppers on 1800 333 000.