A Napoli fan was taken to hospital with facial injuries after being assaulted following the Italian side's defeat by Liverpool at Anfield on Tuesday.
Merseyside Police were contacted at 22:50 GMT after reports of a disturbance involving a group of males in Everton Valley, near to Anfield.
Police received reports that a 26-year-old man, believed to be a Napoli fan from Essex, was assaulted.
Liverpool won 1-0 to progress to the Champions League knockout stages.
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Inquiries into the incident are ongoing.
In April, Liverpool fan Sean Cox was left in a coma after being attacked outside Anfield before the Champions League semi-final against Roma.