"On the scan, his Achilles is clear," Wenger said of Vermaelen, a £10m signing from Ajax in 2009, in November.
"But as soon as he stays out for a while, it tightens up and he has pain. We don't know the source of his pain.
"I don't know where we go with Thomas time-wise but, at the moment, he cannot play."
Wenger is also without captain Cesc Fabregas (hamstring) and fellow midfielder Abou Diaby (ankle) as he prepares for Wednesday's Champions League game against Partizan Belgrade, which the Gunners need to win to guarantee progress to the knock-out stages.
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