Police are investigating an assault outside a licensed premises in St Kilda on 13 March.
Investigators have been told a 41-year-old man left the premises just after 8pm and was standing on the corner of Grey and Barkly Streets.
He struck up a conversation with two unknown males which turned into a physical altercation.
The victim pushed one of the males away before that male struck him to the face causing him to fall back, hitting his head on the ground.
The offender, who was wearing a black long sleeve top, shorts and work boots, and his friend then left on foot south on Barkly Street.
Investigators have released an image of a man who may be able to assist with their enquiries.
Anyone with information that could assist police with their enquiries is urged to contact Crime Stoppers on 1800 333 000 or file a confidential report at www.crimestoppersvic.com.au