I think Williams is the RB. The other 3 I am not sure. Its Wingert vs Brovsky, and I personally have liked Wingert better. Brovsky seems a little slow in getting back and doesn't make enough smart choices. Wingert is just a touch too slow.
As for Central defense, this is the most complicated. I think Hernandez is the best organizer but he seems too slow or something. Mendoza is awesome but he seems to get too far up too often, and he has lost the ball A LOT in dangerous positions. Not sure what the answer is yet.