The man in his 50s was attacked by the group with a glass bottle on March 2.
It was reported to have taken place between 10.50pm and 11.20pm.
Officers retrieved a broken bottle at the scene in Lower Bannister Street, Southampton.
The victim suffered serious injuries, including including a fractured skull and a brain bleed.
He was rushed to Southampton General Hospital, but has since returned home.
The assault happened after a Premier League football match between Southampton and West Ham United, with Hampshire police suspecting a possible altercation took place at the Giddy Bridge pub, on London Road.
Rebecca Stevens, from the Western Investigations Department, said: ‘Prior to this incident, the victim attended the Southampton vs West Ham United football match. He later attended the Giddy Bridge pub on London Road.
‘We believe those involved in the incident had also been at this pub and that there was possibly an altercation that took place while they were there.
‘If you have any information that can help us identify these three men, please contact us.’
Police have released CCTV images of three men they wish to speak to in regards to the assault, who were seen in the area at the time.
A statement from Hampshire Constabulary said: ‘One of the men is described as white, in his 20s, six ft tall, and with a stocky build.
‘The other two men are described as white, in their 20s, and with slim builds.’
Anyone with information is advised to call 101, quoting 44220085815.