The 25-year-old, who completed the 90 minutes at Stamford Bridge despite the injury, is expected to be out until the new year after scans revealed a knee ligament problem.
Wenger was shocked to learn the extent of Ozil’s injury after he was sent back to London from international duty with Germany for further tests last week.
“He had a little problem just before he went out at half-time. He had a little pain with his knee, he felt a crack,” Wenger told beIN Sports.
“I said to our physio to keep an eye on him and if there was anything wrong with him, tell me because when you’re 1-0 down, you want to keep your offensive players on the pitch.
“I am deeply shocked. He wasn’t involved in a collision with anybody.
“It was just after making a pass with the outside of his foot that he injured his leg so it’s very hard to believe that you can damage your ligament with just making a simple pass and it’s very difficult to take that he will be out for a while.”
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