The Spain captain is known to be unsettled at the Bernabeu after losing his automatic place in the first team under Jose Mourinho and the Gunners are keeping a close eye on his situation.
Although Arsene Wenger is keen on Casilllas, the stumbling block could be his price. Casillas is 32 and ever-prudent Arsenal do not want to pay big money for a move knowing full well they cannot sell him on.
They would consider a fee of around £8million but fear Madrid would not listen to offers below the £15m mark.
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