A 51-year-old male was headbutted to the face during the attack which happened outside the Jamhouse on Queen Street, Edinburgh at around 2.50am on Sunday 11th October 2015.
Detectives are keen to trace the man pictured in the CCTV footage and anyone who recognises the man in the images is asked to contact police immediately.
Detective Constable Carole Sneddon said: “The victim suffered a painful injury which required stitches and is likely to result in a permanent scar.
“The man pictured is believed to be of significance to our investigation and anyone who can assist in tracing him is asked to come forward. Similarly we would ask this man to get in touch with police themselves and help with our investigation.”
Those with information can contact Gayfield CID on 101 or the charity Crimestoppers in complete anonymity on 0800 555 111.