A 35-year-old man, believed by police to be an Oldham supporter, was assaulted just outside Anfield after Liverpool's 2-0 FA Cup third-round win over the League One side on Sunday.
The victim was transported to the Royal Liverpool Hospital after flagging down an ambulance on Lower Breck Road, but his injuries are not thought to be life-threatening.
A Merseyside Police statement read: "Merseyside Police is appealing for information after a man was assaulted in the Anfield area of Liverpool on Sunday 5th January, following the FA Cup third-round tie between Liverpool and Oldham Athletic.
"Officers were on routine patrol on Lower Breck Road, at around 5.15pm, when a 35-year old man, who is believed to be an Oldham supporter, flagged down a passing ambulance following a disturbance.
"He was taken to the Royal Liverpool University Hospital where he is receiving treatment for a stab wound. His injuries are not thought to be life threatening.
"The area is being forensically examined and inquiries into the incident are being carried out.
"Detective Chief Inspector Andy O'Connor said: "I want to reassure people that we are conducting a thorough investigation to establish the full circumstances surrounding the incident.
"This was a nasty assault which has left a man in hospital.
"The area was very busy with both football fans and passing motorists when the incident took place and I'm confident some people will have seen what happened."
