The Daily Mail says the central defender has aggravated a lower back injury and was likely to miss the beginning of the new campaign.
Wenger confirmed: "He had a back problem. He came back with it and couldn't practice until now. We don't know how long he will be out for. There is nothing behind that at all.
"Will he stay as captain? It depends. I cannot stick with him now because I think he will miss the start of the season.
"But certainly he will still be the club captain."