A man wearing a Northampton Saints jacket suffered a dislocated shoulder after he was assaulted.
The 51-year-old victim was walking along Butts Road in the direction of Limefields Way in East Hunsbury when he was approached by a man who punched him in the face, causing him to fall.
As a result he suffered a fractured, dislocated shoulder.
The offender quickly ran away. He is described as slim and was wearing dark clothing and blue jeans. The assault happened at around 7pm on Saturday, 19 March.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555111.