The Arsenal manager revealed the Sweden midfielder, signed on loan from Spartak Moscow, has suffered a micro-fracture in his back that could keep him out until mid-March
Wenger revealed that the former Lyon midfielder, who was signed as cover for the injured Aaron Ramsey and suspended Mathieu Flamini, will now be out until mid-March at the latest but the cost of the Swede’s wages will be shared with his parent club.
"He arrived here and fell on his back two days before. First of all it's very difficult to identify a player who can come in of that stature on a free loan.
"We made a medical of his back and found out he had a little microfracture. We have all played with microfractures.
"Then Spartak Moscow accepted to share the costs. As long as he's injured, they pay.
"I had a decision to make. I take nobody or Kallstrom, on Friday after 5 o'clock."
Asked whether he considered pulling the plug on the Kallstrom deal, Wenger added: "Of course it crossed my mind. I would not have signed him if I had two or three more days but it was 5pm.
“At some stage you have to make a decision. You will only know at the end of the season whether it’s right or wrong.”