If you want a winger play a winger not a full back as a wing back. When you get back three you lose a midfield player, who is creative, so you are a man short on the rest of the pitch to shore up the defence. You can't expect full back to be as creative as wide midfielders or wingers. I've no idea why Warnock chose to play 5 at the back yesterday, we look much better with a back 4 and the extra man in midfield.