And pub revellers could hold vital clues in the hunt for the "heavily tattooed" attacker.
Police are urging party-goers who were in the city centre venue at the time of the attack to come forward.
Detectives have stepped up their hunt for the suspect, who attacked the 38-year-old man in Pivo Pivo at the weekend.
The victim was left with "several broken bones in his face" during the horrific attack.
It took place shortly before 11pm on Saturday at the Waterloo Street music venue.
Police believe the pub would have been busy at the time of the incident, and witnesses have been asked to contact detectives with any information about the vicious attack.
Detective Constable David Copeland, of Stewart Street police office, said: "If you saw a disturbance at Pivo Pivo at around 10.50pm on Saturday, April 26, please get in touch."
The victim received treatment for serious facial injuries at hospital before being released.
Police believe the description of the culprit - including his "distinctive" tattoos - will help catch him.
He is described as white, Scottish, around 6ft and with dark hair.
Police said he is between 25 and 35, muscular, with tattoos completely covering his left arm.
He also has a trimmed beard and was wearing a dark grey, short sleeved, polo shirt, with dark grey trousers and red "converse-style" shoes with white soles.
The suspect was last seen heading west from Hope Street, towards the end of Waterloo Street.
Staff at Pivo Pivo said they are working with the police to trace him.
Anyone with information is asked to call Police Scotland on 101.