Ross Barkley's lawyers say the Everton midfielder was attacked by a stranger during a night out.
A Liverpool police force is investigating the incident, footage of which appeared on social media showing Barkley getting punched in the face.
Law firm Himsworths Legal says in a statement that "Ross was the victim of an unprovoked attack by a stranger who approached himon Sundayevening."
Barkley played in Everton's 4-2 victory over Leicester at Goodison Park hours before the incident.
Merseyside Police say they haven't received a report about an assault but are making inquiries.