The Gunners' need for defensive cover has heightened following a hamstring injury to Kieran Gibbs that will rule him out for the next three weeks.
Manolas is a strong contender to fill the vacancy left by Vermaelen.
And Arsenal are pushing hard to complete a £6.5million deal by September 1.
The North London club believe Olympiakos will sell their highly-rated defender, who played for Greece during the World Cup.
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