Police are interested in speaking to the pictured man in connection with the Church Street assault which took place around 3:40am on Sunday November 5.
A 38-year-old man suffered a broken arm when he became involved in an altercation with two men.
The pair started grappling with the man before the victim and one of the men fell to the floor. The offenders fled the scene.
The victim was taken to hospital for treatment.
One of the offenders is described as 5ft 10in to 5ft 11in tall, of slim build with a dark fringe. He was wearing a grey and white hooded top.
A second man is described as white, 5ft 9in tall, of large build with short brown hair.
More: Man has elbow shattered in Church Street brawl
Det Sgt Andrew Crook, of Lancashire Police, said: “The victim of this attack suffered a severe arm fracture which is potentially life changing.
“We’re looking for any information which could help us identify the offenders. If you recognise the man in the picture, please contact us immediately.”
Anyone with information can contact police on (01772) 209796 quoting crime reference SA1717532.
Alternatively you can contact independent charity Crimestoppers anonymously on 0800 555 111 or online at Crimestoppers-uk.org.