At 9.30pm on April 24 the victim was in a William Street bar when he got into an argument with another man.
He was then assaulted and knocked unconscious on the ground.
The victim received significant facial injuries including a broken nose and fractures to his cheekbone.
Police would like to speak to a man in the bar at the time who they believe can assist with their inquiries.
He is described as having fair skin, in his late 30s to 40s, with a stocky build and a short/shaven haircut.
He was wearing a white collared long sleeved shirt, with blue jeans and white/dark coloured sneakers.
Anyone with information can call Crime Stoppers on 1800 333 000.