The 19-year-old was impressive last season for the Gunners and he earned numerous call-ups to the Three Lions’ squad, but has not figured in any games this season and is set to be out for at least two months.
An injury picked up just in England's match against Switzerland in June has been earmarked by Arsenal manager Arsene Wenger as the cause of the playmaker’s current problems.
Capello, however, has questioned why the youngster went on holiday for a month after the game instead of receiving treatment for the injury.
“He suffered this accident against Switzerland, it's true, and afterwards he went on holiday,” he told reporters.
“After, he started the season and was not fit. Now they've found the problem.
“It's not my job to say what happened, but he suffered against Switzerland and then went on holiday for a month.”
The Italian coach, 65, defended his use of the midfielder in the Group G qualification match, saying he would not have risked him if he thought he was not able to play.
Capello added: “He's a really important player for both. Look, I want to explain: when I selected him, he was fit. During the game, it can happen.
“People get shoulder, knee, head injuries. It happened. When he played he was fit. When he started the game he was fit. If he wasn't fit, he wouldn't have played. That's the big difference.”
Wenger has had a number of disagreements with the FA over the years, most recently over the possibility of Wilshere’s inclusion in the squad for this summer's European Under-21 Championships, which he was ultimately withdrawn from.