Wilshere received lengthy treatment after a heavy collision with Denmark captain Daniel Agger early in the game at Wembley on Wednesday, but went on to play almost an hour before being substituted.
The initial prognosis on the injury was positive, with the 22-year-old thought to have only suffered bruising to his left foot, but his club Arsenal announced on Thursday announced the midfielder will be out for around six weeks with a hairline fracture.
"It's always sad when you have a player come from a club, use him on international duty and he gets an injury," the former Fulham and Liverpool boss told Sky Sports News.
"It's very sad and disappointing for Jack and Arsenal, but unfortunately these things happen.
"It was an honest challenge but he took a nasty kick and I can only hope he recovers as early as possible."
