Wilshere, who broke down during pre-season and has not played since, underwent surgery on a stress fracture yesterday after attempts to let it heal naturally failed.
The Gunners later said the midfielder (inset), who emerged last season as a key figure for both club and country, is expected to be out for as long as five more months.
“The initial indications are that the surgery has been successful and Jack will now undergo a prolonged period of rehabilitation,” Arsenal said in a statement. “It is envisaged that Jack’s rehabilitation will take a period of four to five months.”
It is a bitter blow to Arsenal, who are already enduring a very difficult start to the season and could desperately use Wilshere’s drive and creativity. They are tipped to be in a three-way scrum for fourth place, and a lucrative Champions League spot, with Liverpool and north London rivals Tottenham.
Before Saturday’s defeat of 10-man Bolton they languished in 17th place, and have suffered demoralising reverses at Manchester United and Blackburn this term.
Manager Arsene Wenger is also already without two of his most creative players from recent seasons, after selling Cesc Fabregas and Samir Nasri in the summer.
His setback will also come as a concern to England head coach Fabio Capello, with next summer’s European Championships on the horizon.
Wilshere, 19, is projected to be fit for the tournament but will have, at best, the final three months of the season in which to achieve form and fitness.
He will miss next month’s final Euro 2012 qualifier in Montenegro – England’s final competitive fixture before next summer.
Wilshere last played in late July against New York Red Bulls in the Emirates Cup, when he limped off early on with pain in his ankle.
Wenger, who considered it minor at the time, has blamed it on a knock he picked up playing for England against Switzerland in June.
England boss Fabio Capello, in turn, insists Wilshere has a weak spot on his ankle owing to another injury two years ago.
Wilshere had been wearing a protective boot in an attempt to cure the problem through rest, but revealed on Friday night that he would need surgery after all.