I think a huge factor in the left-back conundrum is the fact O'Neill has decided on more or less his best midfield and it doesn't feature any wingers. In that light, you need either Brady or Ward at left-back because, as you mentioned, it gives balance when you've got little other natural width. Like them as LBs or not, they're both quick and naturally athletic, like Coleman, where Wilson or Clark aren't really.
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