It was confirmed by the Football Association today that the 20-year-old has withdrawn from the squad to return to Aston Villa for treatment.
"Jack picked up a knock in training," Southgate told reporters. "We are hopeful it is not too serious but we didn't think he would be ready for the game and we wanted to give Aston Villa the opportunity to get him ready for the weekend. We are hopeful it is not too bad."
The Young Lions will face Norway in a European qualifier in Colchester tomorrow.