Arsenal legend Martin Keown has instructed Mikel Arteta to stop experimenting with Granit Xhaka at left-back ahead of the vital second leg with Villarreal.
The Gunners' 2-1 defeat in Spain on Thursday leaves their Europa League semi-final finely poised, as they have an away goal to take into the return fixture at the Emirates.
Villarreal set out to exploit Arsenal's weakness on the left of defence and it took just five minutes for them to take the lead after Samuel Chukwueze surged past Xhaka to set up Manu Trigueros.
Xhaka - a natural midfielder - has been filling in at left-back in recent weeks after Keiran Tierney suffered a substantial knee injury.
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