Two Arsenal stars ruled out as midfield duo set for fitness tests ahead of West Ham clash
Laurent Koscielny is out of Wednesday's London derby after coming off at half-time during Arsenal's 2-2 draw with Manchester City on Sunday.
Arsene Wenger confirmed the France defender's expected absence at his press conference this morning.
The French manager also revealed that Alex Oxlade-Chamberlain and Aaron Ramsey could return to the Gunners squad after missing out on the City clash.
"Chamberlain and Ramsey have a test today. There is a good chance they are back in the squad.
"Apart from that we lose Koscielny. For how long? I don't know.
"It could be a few weeks, or he could be available against Crystal Palace. He has a scan today. I can tell you much more tomorrow."
Petr Cech remains sidelined after a calf strain ruled him out of the weekend's action but Wenger says the keeper might be available for Monday's trip to Selhurst Park.
Wenger also continued to play coy on his future at the north London club after reporters quizzed him on a potential new deal.
"I have answered that question many times. You ask again. Don't worry, you will get that (answer) soon."
The 67-year-old seemed irritated by questions on the future of Alexis Sanchez, whose contract is up at the end of the 2017/18 season.
"He has one-and-a-half years (left on his) contract. I don't understand that debate.
"Our job is to perform as long as we are there. I do not understand this kind of anxiety. It is absolutely denying what a professional guy is about."