I think the problem is both of the left side positions. Mattock did a decent job on the wing, and Chambers was ok at left back, but a number of times because of the fact that he wanted to use his right foot and the same was true of Newton when he was playing on the left.
Porter was fairly anonymous when and the young lad (Rowe-Turner?) looked a little out of his depth when he came on at left back, although he did get a big cheer when he took the ball off of Lua-Lua.
We need a left back and left winger as a matter of urgency.