“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.”
In a statement, Merseyside Police said it was appealing for witnesses “after a 27-year-old man was assaulted and had his watch stolen in the early hours of Sunday June 28.
“The man suffered stab wounds to his buttocks and head during the incident. He was taken to hospital for treatment for his injuries which are not believed to be life-threatening,” added the statement.
“The investigation is in the early stages but we are determined to find the people responsible for this assault and robbery and I would urge anyone who knows anything to come forward,” said Detective Sergeant Richie Shillito.
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.