A 17-year-old suffered multiple injuries including two broken front teeth and a fractured cheek bone during an attack in Southampton.
He had just got out of a car near the junction of Western Esplanade and Harbour Parade at 0255 BST on Saturday, when three men approached him.
As he spoke to them, another man walked past and punched him, police said.
The suspect and the group of men then fled. Police have released a CCTV image of three men they want to speak to.
The victim was treated at Southampton General Hospital.