“Andre Wisdom has been the victim of an unprovoked assault and robbery,” said a statement from Derby.
“He sustained injuries which resulted in him being admitted to hospital, where he is in a stable condition.
“Merseyside Police are investigating and the club will focus its efforts on supporting Andre and his family.”
Merseyside Police did not immediately respond to CNN Sport’s request for comment.
Wisdom played in Derby’s 2-1 victory against Reading on Saturday.
He signed for the club from Liverpool after a series of loan spells and has made 20 appearances so far this season.
Derby has an outside chance of making the Championship playoffs as the club seeks promotion to the English Premier League.