The Gunners were already without the suspended Cesc Fabregas, and the international break has not been kind.
Abou Diaby is also struggling with a back problem and experienced Brazilian Gilberto faces a long return trip from South America.
The Arsenal manager admits he will have to utilise his squad to the full, so the likes of Denilson and Lassana Diarra are set to be in contention as the Gunners look to extend their unbeaten run to 28 games.
Wenger told arsenal.com: "Hleb came back with a hamstring injury, so once again we lose someone during this [international] period. I think he'll be out for 21 days.
"Flamini came back with a little thigh problem too. That will be one week maximum."
Wenger added: "Gilberto will return very, very late. In fact he only comes back on Friday. So, as for the rest of the squad, we'll see."