Well, it's always good to have options. Sledge and O'Shea are capable of playing as fullbacks, so if O'Dea improves it still gives us options.
O'Dea is certainly not a left-full though. I've always been impressed when I've seen him in the centre, but his lack of pace makes him a liability out wide.
Glad to see that Mowbray recognizes this and seems to be using him in the centre in pre-season.