A man suffered a broken cheekbone when he was punched in the face at Sheffield railway station.
British Transport Police believe the 57-year-old was attacked by a member of a group of Sheffield United fans who had returned from an away fixture.
PC Stephen Slocombe said: “As the group passed Café Ritazza heading towards the taxi rank, the man was assaulted.
“The victim sustained a broken cheekbone in the attack. He has had to have a metal plate fitted.
“This was a vicious and completely unprovoked attack and it is vital we find the person responsible.
“He was among a group who witnessed the assault and we would appeal to them and anyone else who saw what happened to come forward.”
Anyone with information about the incident on Saturday, March 19 should call 0800 405040.