The 21-year-old had to be replaced by Eduardo after 37 minutes as the Gunners eventually strolled to a 3-0 win against Tottenham Hotspur.
"It was a serious one and we go into a period where you need all your players," admitted a concerned Wenger.
"It's a shame that we lost him today and I am quite scared that he will be out for a while. It is a groin injury and I am scared it could be three or four weeks."
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Of his side's display, Wenger added: "We took advantage of the shock of the first goal and in the second half we always played a little restricted.
"After the third there wasn't the impression that Spurs would come back.
"I threw my jacket down because I was frustrated, I couldn't communicate with the players because of the noise of the stadium - I am not used to that!"