Wilshere played on following treatment until he was replaced on the hour, and afterwards maintained it was "just a bruise" when he spoke to reporters, having been initially assessed by the Football Association.
It is understood the fracture was so minuscule that the scanning equipment within Wembley failed to detect the issue following a precautionary examination by England's medical staff, and i t was only when Arsenal conducted a more detailed test of the injured area that the real problem became more apparent
"Following initial scans carried out by the FA on Wednesday night, further investigation by Arsenal's medical team has discovered a crack to a small bone in Jack's left foot - the navicular, an area of his foot which has not been previously injured
Jack will now require a period of approximately six weeks' rehabilitation, before starting to regain his match fitness," a statement from Arsenal read.
While Arsenal are understood to be naturally disappointed by the turn of events, they remain positive Wilshere will be able to return to play some part in the final few matches - unlike forward Theo Walcott, whose own World Cup dream was shattered by a serious knee injury in January.
Although Wilshere's place in the World Cup squad - a provisional 30-man party set to be named on May 13 - does not look initially in any serious jeopardy, the midfielder is nevertheless now set to miss at least eight club fixtures - starting with Saturday's FA Cup quarter-final against Everton and then next week's second leg of the Champions League last-16 tie away to Bayern Munich.
Although it will be of little comfort, Arsenal will be compensated financially for the injury and the Barclays Premier League club will not have to pay for the midfielder's wages - reported at around some ?100,000-per-week - while he is sidelined.
That money will not come from the FA, but from the organisation's insurers to protect against such potentially vast payments.
England manager Roy Hodgson has expressed his sympathy for both player and club.
"It is always sad when you have a player come from a club, use him on international duty and he gets an injury, but unfortunately these things happen," he said at the London Football Legends Awards on Thursday evening
"It was an honest challenge, but he took a nasty kick and I can only hope he recovers as early as possible."
Wilshere insisted there would be no hard feelings between himself and Agger
"It was one of them - we were both going to go in for it and unfortunately I was the one who came out a little bit worse."
Source : PA
Source: PA