I agree it was a mistake by Oscar should have put Calderon in the centre and played Chicksen at right back and left Ward as he was but for me Chicksen is ok getting forward but has a lot to learn about defending before he is the regular left back.
Whilst not the sole reason we lost at Derby, Chicksen coming on at left back and losing Wards attacking greatly contributed to our defeat and the manner of it. I think that Chicksen has promise but is a long way off defensively to be our regular left back.