A 19-year-old was left with dangerous head injuries after being punched to the ground near the rear entrance of Junk, in Bedford Place.
Shortly after midnight on the morning of Friday 30th August, the victim, from Locks Heath, was knocked down on the corner of Winchester Street and Salisbury Street. It is believed that the attacker then became involved in a larger fight with several other people.
The victim was treated at Southampton General Hospital, where staff found he had suffered a bleed on the brain.
Detectives are searching for a group of Asian men that they believe were in the area and could have been approached by the offender and his companions. They are also looking for a couple who were seen leaving Junk at the time of the incident: a woman with long blonde hair wearing a short skirt or shorts, and the man with her.
Anyone with information is asked to contact Detective Constable Abigail Leeson at Shirley CID on 101, or to ring the Crimestoppers line on 0800 555 111.