If we'd kept Walker and got Naughton on the other side, there might be a rationale for it. However, the main reason that it would not be right is that the current trend for teams to play with one recognised striker would mean that the back 3 would be marking one guy. As said above, that would mean we'd be light elsewhere around the pitch.
Our current plight lies in midfield: deal with that and the existing back four doesn't look quite as bad as you make out, ASHTON.
For mobile, tenacious midfielders in our current squad who wouldm cover the fullbacks, Hogg would be the best bet; but - judging on pre-sesaon line-ups - McGinge doesn't seem to agree.