Arsenal defender Philippe Senderos will miss the first two months of the season with the injury he suffered on World Cup duty.
Swiss international Senderos dislocated his shoulder against South Korea on 23 June and the Gunners' medical team believe he could be sidelined until late October.
That would rule the 21-year-old out of the opening 13 games of the season, including the September 17 showdown with Manchester United and Arsenal's Champions League qualifier.
With Sol Campbell having departed recently, Senderos' injury has left Wenger short on options in defence and the Frenchman admits he might be forced into the transfer market to find a replacement.
"We have lost Senderos for the next three months. Johan Djourou and Gael Clichy have had injuries as well," he told the club's official website, www.arsenal.com.
"If we find a player who can play centre back and left back then we are still open for transfers."
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