#3 Shkodran Mustafi
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Mustafi is Arsenal's most expensive defender in its rich history but his performance has never ever been consistent. The club failed to offload him during the previous transfer window and his recent performances surely haven't done much to change their minds. His horrendous defending on Sergio Aguero's opening goal at Wembley shows how inconsistent he has been, after arriving at Arsenal.
Though he has all the natural attributes to be an exceptional center back, he has been positionally exploited way too many times. His inconsistency has had a huge impact on Arsenal's dismal performances away from home this season. We won't write him off completely, but he needs to learn from his mistakes and be much much more lethal at the back and very quickly or he will definitely be shown the way out of Emirates.