Arsenal defender Per Mertesacker has undergone surgery on his ankle injury and will be out "long term", according to manager Arsene Wenger.
Mertesacker suffered ligament damage during Saturday's 2-1 victory at Sunderland and could be sidelined for the rest of the season.
"Unfortunately he has had surgery and we have lost him for a while," Wenger told the club's official website, www.arsenal.com. "How long I don't know. He had reconstruction of his ligaments, so it will be long term."
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