With Cesc Fabregas and Samir Nasri rumoured to be on their way, Wenger could do with the England youngster being fit for the start of the season.
But he told arsenal.com: "Jack Wilshere has been put in a boot.
"He has an inflamed ankle and it is difficult to set any specific date on his return, but we hope he will be back soon."
On another midfielder on The Emirates casualty list, the Frenchman added: "Abou Diaby is slowly improving. As well, it is difficult to say when he will be back, but we know he will not play before the end of September."