“Andre Wisdom was the victim of unprovoked assault and robbery,” said a Derby statement.
“He suffered injuries which led him to hospitalization, where he is in stable condition.
“Merseyside police are investigating and the club will focus its efforts on supporting André and his family.”
Merseyside police did not immediately respond to CNN Sport’s request for comment.
Wisdom played in Derby’s 2-1 victory over Reading on Saturday.
He has signed for the Liverpool club after a series of loan periods and has made 20 appearances so far this season.
Derby has an outside chance of qualifying for the championship playoffs as the club seeks promotion to the English Premier League.