Wisdom was representing the Rams as recently as Saturday and subsequently visited a family member in Toxteth, Liverpool.
As he made his way back to the car, he was assaulted, resulting in a hospitalisation. He is in a stable condition.
A Derby statement reads: "Derby County Football Club can confirm that Andre Wisdom has been the victim of an unprovoked assault and robbery.
"He sustained injuries which resulted in him being admitted to hospital, where he is in a stable condition.
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"Merseyside police are investigating and the club will focus its efforts on supporting Andre and his family. Therefore we will not be making any further comment at this time."
Wisdom came through the ranks at Liverpool and left for Derby in 2017, having previously spent time at the club on loan from Anfield.