Wenger stressed he was looking to strengthen, especially in midfield, with Mikel Arteta and Abou Diaby both also sidelined.
"We tried to bring one in, but we are working on that. You have to understand there is still a long way to go," he said.
"The transfer market starts for me now and a lot of activity will happen between now and September 2.
"From August 21 until September 2 you have 12 days, so a lot will happen. It starts now."
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