The 29-year-old was walking between Shelley Road, Worthing, and the rear of TK MAXX in Liverpool Road at about 1am on Friday December 27 when he had his wallet and mobile phone stolen by two men.
He was walking towards the Tesco Express in Chapel Road to see if it was open when he was asked for a cigarette by an unknown man.
When the victim told him he did not have any, he was kicked and punched by the man who was joined by a second man, and had his mobile phone and wallet stolen.
He sustained a suspected broken cheekbone and is having ongoing medical treatment.
The man was seen shortly afterwards by patrolling police unit who searched the area and spotted two suspects nearby, but they ran off towards Liverpool Gardens and disappeared.
Detective Constable Andy Hobden said; “This is an unprovoked attack, causing a nasty injury. We are very keen to find these men. If anyone has any information about the incident please contact us via 101 or email email@example.com quoting serial 0078 of 27/12. You can also call the independent charity Crimestoppers anonymously on 0800 555 111.”