The Egyptian international was forced to leave the pitch in the 34th minute with his team trailing 1-0 at the Maktoum bin Rashid Stadium in Dubai on Monday.
"According to medical reports, Zidan will be out for about four to six weeks," a spokesman for the club said. "It is indeed a huge setback so early in the season.
"However, injuries are something that we cannot do anything about. We can only hope he recovers quickly and get back to action."
Zidan, a prolific scorer in Germany's Bundesliga for Werder Bremen, Mainz and Borussia Dortmund before his move to the Abu Dhabi club on a two-year contract, took just five minutes to score for his new team in the 2-1 win over Al Dhafra in their Etisalat Cup opener last week.
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