Police are investigating an assault that took place on Sydney Road, Brunswick on 6 March, Victoria Police say.
It is believed the victim approached two men about 1am and had a brief conversation before one of the offenders elbowed him.
Investigators have been told the 42-year-old man was knocked unconscious and fell backwards into a sign and onto the footpath.
The offender and associate remained in the area for about a minute before leaving.
The offender is perceived to be Caucasian in appearance, aged in his late 30s or early 40s with a solid build and short dark hair.
The associate is described as being aged in his 40s, with a full beard and dark wavy hair.
Investigators have released images of two men they believe can assist with their enquiries.
Anyone with information is urged to contact Crime Stoppers.
